This nonprovisional application claims the benefit of U.S. Provisional Application(s) No. 60/059,989, 60/059,992, 60/060,022, 60/060,076 and 60/060,677 all filed Sep. 25, 1997.
The present invention relates to an exposure apparatus and an exposure method for exposing a sensitive substrate with a laser beam, an electron beam and other charged particle beams. In particular, the present invention relates to an exposure apparatus and an exposure method, which is used for producing semiconductor elements or liquid crystal display elements by means of the photolithography process, and which exposes the sensitive substrate by projecting a pattern formed on a mask via a projection optical system onto the sensitive substrate. Especially, the present invention relates to an exposure apparatus and an exposure method suitable for performing exposure and alignment of two substrates in parallel using two substrate stages.
Various exposure apparatuses have been hitherto used, for example, when semiconductor elements or liquid crystal display elements are produced by means of the photolithography step. At present, a projection exposure apparatus is generally used, in which an image of a pattern formed on a photomask or reticle (hereinafter generally referred to as xe2x80x9creticlexe2x80x9d) is transferred via a projection optical system onto a substrate (hereinafter referred to as xe2x80x9csensitive substratexe2x80x9d, if necessary) such as a wafer or a glass blade applied with a photosensitive material such as photoresist on its surface. In recent years, a reduction projection exposure apparatus (so-called stepper) based on the so-called step-and-repeat system is predominantly used as the projection exposure apparatus, in which a sensitive substrate is placed on a substrate stage which is movable two-dimensionally, and the sensitive substrate is moved in a stepwise manner (subjected to stepping) by using the substrate stage to repeat the operation for successively exposing respective shot areas on the sensitive substrate with the image of the pattern formed on the reticle.
Recently, a projection exposure apparatus based on the step-and-scan system (scanning type exposure apparatus as described, for example, in Japanese Laid-Open-Patent Publication No. 7-176468, corresponding to U.S. Pat. No. 5,646,413), which is obtained by applying modification to the stationary type exposure apparatus such as the stepper, is also used frequently. The projection exposure apparatus based on the step-and-scan system has, for example, the following merits. That is, (1) the projection optical system is easily produced because a large field can be exposed by using a smaller optical system as compared with the stepper, and a high throughput can be expected owing to the decrease in number of shots because a large field is exposed. Further, (2) an averaging effect is obtained owing to relative scanning for the reticle and the wafer with respect to the projection optical system, and thereby it is possible to expect improvement in distortion and depth of focus. Moreover, it is considered that the scanning type projection exposure apparatus will be predominantly used in place of the stepper, because a large field will become essential in accordance with the increase in the degree of integration of the semiconductor element, which is 16 M (mega) at present and will become 64 M for DRAM, 256 M, and 1 G (giga) in future as the progress proceeds along with times.
With this type of projection exposure apparatus, alignment between the reticle and the wafer needs to be performed highly precisely prior to exposure. To carry out this alignment, the wafer is provided with a position detecting mark (alignment mark) formed (or exposure transferred) by a previous photolithographic process. By detecting the position of this alignment mark, the exact position of the wafer (or a circuit pattern on the wafer) can be detected.
Alignment microscopes for detecting the alignment mark are roughly classified into the on-axis type for detecting the mark through a projection lens, and the off-axis type for detecting the mark without allowing the detecting light pass through a projection lens. With regard to a projection exposure apparatus with an excimer laser light source, which would be predominant in this field, an alignment microscope of the off-axis type is optimal. This is because the projection lens has been corrected for chromatic aberration due to exposure light, so that the on-axis type cannot condense alignment light, or if it could, an error due to chromatic aberration would be marked. An alignment microscope of the off-axis type, on the other hand, is provided separately from the projection lens; therefore, free optical design is possible without regard for such chromatic aberration, and various alignment systems can be used. For example, a phase contrast microscope or a differential interference microscope may also be used.
When the sensitive substrate is subjected to exposure by using the scanning type projection exposure apparatus, the so-called complete pre-measurement control method has been carried out as follows as described, for example, in Japanese Laid-Open Patent Publication No. 6-283403 corresponding to U.S. Pat. No. 5,448,332. That is, all detecting points included in one array provided on a front side in the scanning direction with respect to an exposure field are used as sample points. All values of focus positions at the sample points are previously measured before exposure, followed by the averaging process and the filtering process. The autofocus and the autoleveling mechanisms are controlled in an open manner during the exposure in consideration of phase delay. Concurrently with the foregoing operation, an inclination in the non-scanning direction is determined by means of the least square approximation method from the measured values of the focus positions at the respective sample points in the one array described above to perform the leveling control in the non-scanning direction in accordance with the open control.
Such a projection exposure apparatus is principally used as a mass-production machine for semiconductor elements or the like. Therefore, the projection exposure apparatus necessarily required to have a processing ability that how many sheets of wafers can be subjected to the exposure process for a certain period of time. That is, it is necessarily required for the projection exposure apparatus to improve the throughput.
In this context, in the case of the projection exposure apparatus based on the step-and-scan system described above, when a large field is exposed, the improvement in throughput is expected because the number of shots to be exposed on the wafer is decreased as described above. However, since the exposure is performed during movement at a constant velocity in accordance with synchronized scanning for the reticle and the wafer, it is necessary to provide acceleration and deceleration areas before and after the constant velocity movement area. As a result, if a shot-having a size equivalent to a shot size of the stepper is exposed, there is a possibility that the throughput is rather decreased as compared with the stepper.
The outline of the flow of the process in such a projection exposure apparatus is as follows.
(1) At first, a wafer load step is performed, in which a wafer is loaded on a wafer table by using a wafer loader.
(2) Next, a search alignment step is performed, in which the position of the wafer is roughly detected by using a search alignment mechanism. Specifically, the search alignment step is performed, for example, on the basis of the contour of the wafer, or by detecting a search alignment mark on the wafer.
(3) Next, a fine alignment step is performed, in which the position of each of the shot areas on the wafer is accurately determined. In general, the EGA (enhanced global alignment) system is used for the fine alignment step. In this system, a plurality of sample shots included in the wafer are selected beforehand, and positions of alignment marks (wafer marks) affixed to the sample shots are successively measured. Statistical calculation based on, for example, the so-called least square method is performed on the basis of results of the measurement and designed values of the shot array to determine all shot array data on the wafer (see, for example, Japanese Laid-Open Patent Publication No. 61-4449 corresponding to U.S. Pat. No. 4,780,617). In this system, it is possible to determine the coordinate positions of the respective shot areas with high accuracy at a high throughput.
(4). Next, an exposure step is performed, in which the image of the pattern on the reticle is transferred onto the wafer via the projection optical system while successively positioning the respective shot areas on the wafer to be located at exposure positions on the basis of the coordinate positions of the respective shot areas having been determined in accordance with the EGA system or the like described above and the previously measured baseline amount.
(5) Next, a wafer unload step is performed, in which the wafer on the wafer table having been subjected to the exposure process is wafer-unloaded by using a wafer unloader. The wafer unload step is performed simultaneously with the wafer load step (1) described above in which the exposure process is performed. That is, a wafer exchange step is constructed by the steps (1) and (5).
As described above, in the conventional projection exposure apparatus, the roughly classified four operations are repeatedly performed by using one wafer stage, i.e., wafer exchangexe2x86x92search alignmentxe2x86x92fine alignmentxe2x86x92exposurexe2x86x92wafer exchange.
The throughput THOR [sheets/hour] of such a projection exposure apparatus can be represented by the following expression (1) assuming that the wafer exchange time is T1, the search alignment time is T2, the fine alignment time is T3, and the exposure time is T4.
THOR=3600/(T1+T2+T3+T4)xe2x80x83xe2x80x83(1)
The operations of T1 to T4 are executed repeatedly and successively (sequentially) as in T1xe2x86x92T2xe2x86x92T3xe2x86x92T4xe2x86x92T1 . . . Accordingly, if the individual elements ranging from T1 to T4 involve high speeds, then the denominator is decreased, and the throughput THOR can be improved. However, as for T1 (wafer exchange time) and T2 (search alignment time), the effect of improvement is relatively small, because only one operation is performed for one sheet of wafer respectively. As for T3 (fine alignment time), the throughput can be improved if the sampling number of shots is decreased in the case of the use of the EGA system, or if the measurement time for a single shot is shortened. However, on the contrary, the alignment accuracy is deteriorated due to shortened T3. Therefore, it is impossible to easily shorten T3.
On the other hand, T4 (exposure time) includes the wafer exposure time and the stepping time for movement between the shots. For example, in the case of the scanning type projection exposure apparatus based on, for example, the step-and-scan system, it is necessary to increase the relative scanning velocity between the reticle and the wafer in an amount corresponding to the reduction of the wafer exposure time. However, it is not allowed to increase the scanning velocity without consideration because the synchronization accuracy is deteriorated.
With the apparatus using an off-axis alignment microscope, such as the projection exposure apparatus with the excimer laser light source which would be predominant in this field, it is not easy to improve the controllability of the stage. With this type of projection exposure apparatus, there is need to precisely control the position of the wafer stage, without Abbe""s error, during exposure of the mask pattern through the projection optical system and during alignment, thereby to achieve highly precise superposition. For this purpose, it is necessary to set a constitution in which the measuring axis of the laser interferometer passes through the center of projection of the projection optical system and the center of detection of the alignment microscope. Furthermore, neither the measuring axis passing through the center of projection of the projection optical system nor the measuring axis passing through the center of detection of the alignment microscope should be interrupted in the moving range of the stage during exposure and in the moving range of the stage during alignment. To satisfy this requirement, the stage necessarily becomes large in size.
Important conditions for such a projection exposure apparatus other than those concerning the throughput described above include (1) the resolution, (2) the depth of focus (DOF: Depth of Focus), and (3) the line width control accuracy. Assuming that the exposure wavelength is xcex, and the numerical aperture of the projection lens is N.A. (Numerical Aperture), the resolution R is proportional to xcex/N.A., and the depth of focus (DOF) is proportional to xcex/(N.A.)2.
Therefore, in order to improve the resolution R (in order to decrease the value of R), it is necessary to decrease the exposure wavelength xcex, or it is necessary to increase the numerical aperture N.A. Especially, in recent years, semiconductor elements or the like have developed to have high densities, and the device rule is not more than 0.2 xcexcm L/S (line and space). For this reason, a KrF excimer laser is used as an illumination light source in order to perform exposure for the pattern. However, as described above, the degree of integration of the semiconductor element will be necessarily increased in future. Accordingly, it is demanded to develop an apparatus provided with a light source having a wavelength shorter than that of KrF. Representative candidates for the next generation apparatus provided with the light source having the shorter wavelength as described above include, for example, an apparatus having a light source of ArF excimer laser, and an electron beam exposure apparatus. However, the case of the ArF excimer laser involves numerous technical problems in that the light is scarcely transmitted through a place where oxygen exists, it is difficult to provide a high output, the service life of the laser is short, and the cost of the apparatus is expensive. The electron beam exposure apparatus is inconvenient in that the throughput is extremely low as compared with the light beam exposure apparatus. In reality, the development of the next generation machine, which is based on the principal viewpoint of the use of a short wavelength, does not proceed so well.
It is conceived to increase the numerical aperture N.A., as another method to increase the resolution R. However, if N.A. is increased, there is a demerit that DOF of the projection optical system is decreased. DOF can be roughly classified into UDOF (User Depth of Focus; a part to be used by user: for example, difference in level of pattern and resist thickness) and the overall focus difference of the apparatus itself. Up to now, UDOF has contributed to DOF in a greater degree. Therefore, the development of the exposure apparatus has been mainly directed to the policy to design those having a large DOF. Those practically used as the technique for increasing DOF include, for example, modified illumination. the way, in order to produce a device, it is necessary to form, on a wafer, a pattern obtained by combining, for example, L/S (line and space), isolated L (line), isolated S (space), and CH (contact hole). However, the exposure parameters for performing optimum exposure differ for every shape of the pattern such as L/S and isolated line described above. For this reason, a technique called ED-TREE (except for CH concerning a different reticle) has been hitherto used to determine, as a specification of the exposure apparatus, common exposure parameters (for example, coherence factor "sgr", N.A., exposure control accuracy, and reticle drawing accuracy) so that the resolution line width is within a predetermined allowable error with respect to a target value, and a predetermined DOF is obtained. However, it is considered that the following technical trend will appear in future.
(1) In accordance with the improvement in process technology (improvement in flatness on the wafer), the difference in pattern level will be progressively lowered, and the resist thickness will be progressively decreased. There will be a possibility that the UDOF may change from an order of 1 xcexcmxe2x86x920.4 xcexcm.
(2) The exposure wavelength changes to be short, i.e., g-ray (436 nm)xe2x86x92i-ray (365 nm)xe2x86x92KrF (248 nm). However, investigation will be made for only a light source based on ArF (193) in future. Further technical hurdle is high. Thereafter, the progress will proceed to EB exposure.
(3) It is expected that the scanning exposure such as those based on the step-and-scan system will be predominantly used for the stepper, in place of the stationary exposure such as those based on the step-and-repeat system. The step-and-scan system makes it possible to perform exposure for a large field by using a projection optical system having a small diameter (especially in the scanning direction), in which it is easy to realize high N.A. corresponding thereto.
In the background-of the technical trend as described above, the double exposure method is reevaluated as a method for improving the limiting resolution. Trial and investigation are made such that the double exposure method will be used for KrF exposure apparatus and ArF exposure apparatus in future to perform exposure up to those having 0.1 xcexcm L/S. In general, the double exposure method is roughly classified into the following three methods.
(1) L/S""s and isolated lines having different exposure parameters are formed on different reticles, and exposure is performed for each of them on an identical wafer under an optimum exposure condition.
(2) For example, when the phase shift method is introduced, L/S has a higher resolution at an identical DOF as compared with the isolated line. By utilizing this fact, all patterns are formed with L/S""s by using the first reticle, and L/S""s are curtailed for the second reticle to form the isolated lines.
(3) In general, when the isolated line is used, a high resolution can be obtained with a small N.A. as compared with L/S (however, DOF is decreased). Accordingly, all patterns are formed with isolated lines, and the isolated lines, which are formed by using the first and second reticles respectively, are combined to form L/S""s. The double exposure method described above has two effects of improvement in resolution and improvement in DOF.
However, in the double exposure method, the exposure process must be performed several times by using a plurality of reticles. Therefore, inconveniences arise in that the exposure time (T4) is not less than two-fold as compared with the conventional apparatus, and the throughput is greatly deteriorated. For this reason, actually, the double exposure method has not been investigated so earnestly. The improvement in resolution and depth of focus (DOF) has been hitherto made by means of, for example, the use of an ultraviolet exposure wavelength, modified illumination, and phase shift reticle.
However, when the double exposure method described above is used for the KrF and ArF exposure apparatuses, it is possible to realize exposure with up to 0.1 xcexcm L/S. Accordingly, it is doubtless that the double exposure method is a promising choice to develop the next generation machine aimed at mass-production of DRAM of 256 M and 1 G. Therefore, it has been expected to develop a new technique for improving the throughput which is a task of the double exposure method as a bottleneck for such a purpose.
In this context, if two or more operations of the four operations, i.e., the wafer exchange, the search alignment, the fine alignment, and the exposure operations can be concurrently processed in parallel, it may be possible to improve the throughput as compared with the case in which the four operations are sequentially performed. For this purpose, it is premised that a plurality of substrate stages are provided. The provision of a plurality of substrate stages is known, which may be considered to be easy from a theoretical viewpoint. However, there are numerous problems which should be solved in order to exhibit a sufficient effect. For example, if two substrate stages each having a size equivalent to those of presently used substrate stages are merely arranged and placed side by side, an inconvenience arises in that the installation area for the apparatus (so-called foot print) is remarkably increased, resulting in increase in cost of the clean room in which the exposure apparatus is placed. In order to realize highly accurate overlay, it is necessary to execute alignment for the sensitive substrate on an identical substrate stage, and then execute positional adjustment for the image of the pattern on the mask and the sensitive substrate by using a result of the alignment so that exposure is carried out. Therefore, for example, if one of the two substrate stages is merely exclusively used for exposure, and the other is merely exclusively used for alignment, there is no real countermeasure.
Further, there have been hitherto the following necessities. That is, when two operations are concurrently processed in parallel to one another while independently controlling movement of two substrate stages, then the movement should be controlled so that the both stages do not make contact with each other (prevention of interference), and the operation performed on one of the stages does not affect the operation performed on the other stage (prevention of disturbance).
Furthermore, in the case of the scanning type projection exposure apparatus, the order of exposure for respective shot areas on the wafer W is determined, for example, by respective parameters of (1) to (4), i.e., (1) acceleration and deceleration times during scanning, (2) adjustment time, (3) exposure time, and (4) stepping time to adjacent shot. However, in general, the acceleration and the deceleration of the reticle stage give the rate-determining condition. Therefore, it is most efficient that scanning is alternately performed for the reticle stage from one side to the other side and from the other side to one side in the scanning direction, in synchronization with which scanning is alternately performed for the wafer in the direction opposite to that for the reticle stage (for this purpose, the wafer is subjected to stepping in an amount corresponding to one shot after exposure for one shot).
However, when the conventional complete pre-measurement control described above is performed (for example, Japanese Laid-Open Patent Publication No. 6-283403, it has been difficult to perform exposure in the aforementioned most efficient order of exposure. That is, when a shot area in the vicinity of the center of the wafer is exposed, the complete pre-measurement control can be performed without any special problem. However, in the case of shot areas existing in the vicinity of the outer circumference of the wafer, and in the case of incomplete shots existing on the outer circumference, it is sometimes difficult to perform the complete pre-measurement control depending on the scanning direction for such shot areas. In the present circumstances, it is inevitable to direct the scanning direction from the inside to the outside of the wafer in order to perform complete pre-measurement. For this reason, the throughput has been consequently lowered.
Japanese Laid-Open Patent Publication No. 8-51069, corresponding to U.S. patent application Ser. No. 261,630 filed on Jun. 17, 1994, discloses a step-and-repeat apparatus comprising a plurality of wafer stations each of which comprises a wafer position observing and tracking apparatus. The apparatus is provided, as the wafer station, with an image-forming station and a characteristic measuring station, and each station has a chuck for holding the wafer thereon. On the characteristic measuring station, an inclination and a depth of a field is determined for each field of the wafer. The image-forming station is provided with an image-forming lens, and the image is printed on each field of the wafer on which the characteristic has been measured in the measuring characteristic station. To measure the characteristic and form an image in these stations are performed in parallel. This publication discloses that therefore the throughput of this apparatus can be doubled compared with a conventional stepper which performs the measurement of characteristic and the formation of image in order. However, in this type of apparatus, in order that the data concerning the wafer collected on the measuring characteristic station are kept effective and accurate even after the wafer has been transferred to the image-forming station, the wafer must be monitored continuously with an interferometer.
The present invention has been made under the circumstances as described above, and a first object of the invention is to provide a projection exposure apparatus which makes it possible to further improve the throughput.
A second object of the invention is to provide a projection exposure method which makes it possible to further improve the throughput.
A third object of the invention is to provide a projection exposure apparatus which makes it possible to improve the throughput by concurrently processing, for example, the exposure operation and the alignment operation in parallel to one another, miniaturize a substrate stage, and reduce the weight of the substrate stage. fourth object of the invention is to provide a projection exposure method which makes it possible to improve the throughput, miniaturize a stage, and reduce the weight of the stage.
A fifth object of the invention is to provide a projection exposure apparatus which makes it possible to further improve the throughput and avoid any mutual influence of disturbance between the both stages.
A sixth object of the invention is to provide a projection exposure apparatus which makes it possible to further improve the throughput and avoid any mutual interference between the both stages.
A seventh object of the invention is to provide a projection exposure method which makes it possible to further improve the throughput and avoid any mutual influence of disturbance between the both stages.
An eighth object of the invention is to provide a projection exposure method which makes it possible to further improve the throughput and avoid any mutual interference between the both stages.
A ninth object of the invention is to provide a projection exposure apparatus which makes it possible to perform highly accurate focus/leveling control while further improving the throughput.
A tenth object of the invention is to provide a projection exposure method which makes it possible to perform highly accurate focus/leveling control while further improving the throughput.
An eleventh object of the invention is to provide a projection exposure method which makes it possible to perform highly accurate focus/leveling control while further improving the throughput even when EGA is performed for conducting positional adjustment with respect to a mask on the basis of an arrangement of sample shot areas.
A twelfth object of the invention is to provide a projection exposure apparatus which makes it possible to perform highly accurate focus/leveling control while further improving the throughput, such that focus information concerning those disposed at the inside, which has been impossible to be subjected to pre-measurement when shot areas in the vicinity of outer circumference of a sensitive substrate are exposed, is used as pre-measurement data for focus control.
A thirteenth object of the invention is to provide a scanning exposure method which makes it possible to perform highly accurate focus/leveling control while further improving the throughput.
A fourteenth object of the invention is to provide an exposure method capable of improving throughput and determining the size of the substrate stage regardless of the baseline amount.
If a plurality of actions among the aforementioned three actions, i.e., wafer replacement (including search alignment) fine alignment and exposure, can be performed in parallel even partially, throughput may be improved compared with the sequential execution of these actions. The present invention has been devised in this view and for overcoming the inconveniences of the conventional art.
According to the first aspect of the present invention, there is provided an exposure apparatus for exposing a plurality of areas (SA) divided on a sensitive substrate (W1, W2) respectively with a predetermined pattern, the exposure apparatus comprising;
a plurality of stages (WS1, WS2), each holding a sensitive substrate (W1, W2) thereon, while moving independently between a positional information measuring section (PIS) wherein positional information of the respective divided areas on the sensitive substrate are measured and an exposure section (EPS). The measurement of the positional information on the respective divided areas (shot areas (SA)) on the sensitive substrate is performed on the positional information measuring section (PIS), while the exposure of the respective divided areas is performed on the exposure section (EPS). Since the measurement and the exposure are performed in parallel, the throughput is remarkably improved compared to a conventional exposure apparatus wherein the process steps in these sections are performed sequentially. In order for the inventive exposure apparatus to keep accurate the positional information, such as positions in a directions of X, Y and Z of each area, measured in the positional information measuring section, each stage (WS1, WS2) has a reference mark (MK1, MK2, MK3) for determining a relative position of each divided area on the sensitive substrate on the stage. The alignment of each divided area on the sensitive substrate is performed in the exposure section using the relative position of each divided area with respect to the reference mark measured in the positional information measuring section. Accordingly, it is sufficient for each of the position measuring system (such as interferometers) for measuring position of the stage positioned on the positional information measuring section and the position measuring system (such as interferometers) for measuring position of the stage positioned on the exposure section, to independently measure the stage position only in one section. It is not necessary for one of the position measuring systems to monitor the position of one stage during the movement of the stage between the two sections. Further, there is no need to transmit data between the position measuring systems.
The exposure apparatus further may comprise positional information detecting systems in the positional information measuring section and the exposing section, respectively. The positional information detecting systems may measure or determine the position of each divided area of the sensitive substrate with respect to the reference mark. When the exposure apparatus is a projection exposure apparatus, the positional information detecting system in the positional information measuring section may an alignment system (24a, 24b) and a detection system (130) for detecting the position of the surface of the sensitive substrate, and the positional information detecting system in the exposure section may be a detector for detecting the marks through the projection optical system. The exposure apparatus may further comprise a storing apparatus (91) for storing positional information of each divided area on the sensitive substrate which has been determined in the positional information measuring section.
According to the second aspect of the present invention, there is provided a projection exposure apparatus for exposing a sensitive substrate (W1, W2) by projecting a pattern formed on a mask (R) through a projection optical system (PL) onto the sensitive substrates, characterized by having:
a first substrate stage (WS1) which is movable on a two-dimensional plane while holding a sensitive substrate (W1), the first substrate stage having a reference mark formed thereon;
a second substrate stage (WS2) which is movable independently from the first substrate stage (WS1) on the same plane as that for the first substrate stage (WS1) while holding a sensitive substrate (W2), the second substrate stage having a reference mark formed thereon;
at least one mark detecting system (for example, 24a) provided apart from the projection optical system (PL), for detecting reference mark on the substrate stage (WS1, WS2) or a mark on the sensitive substrate (WS1, WS2) held on the substrate stage (WS1, WS2); and
a controller (90) for controlling operations of the both stages (WS1, WS2) so that one of the first and second substrate stages (WS1 or WS2) performs a mark-detecting operation effected by the mark detecting system (24a), while the other stage (WS2 or WS1) performs an exposure operation.
According to the projection exposure apparatus, the controller controls the operations of the both stages (WS1, WS2) so that the one of the stages of the first substrate stage and the second substrate stage performs the mark-detecting operation effected by the mark detecting system, during which the exposure operation is performed on the other stage. Accordingly, the detecting operation for the mark on the sensitive substrate held on the one substrate stage can be processed concurrently with the exposure operation for the sensitive substrate held on the other substrate stage. Therefore, the operation corresponding to the time T2 and the time T3 explained above can be processed concurrently with the operation corresponding to the time T4. Thus, it is possible to improve the throughput as compared with the conventional sequential process which requires the time (T1+T2+T3+T4).
In this projection exposure apparatus, it is still more desirable that when the projection exposure apparatus further comprises a transport system (180 to 200) for delivering the sensitive substrate (W1, W2) with respect to the first and second substrate stages (WS1 and WS2), then the controller (90) controls the operations of the both stages (WS1, WS2) so that one of the substrate stages (WS1 or WS2) performs the delivery of the sensitive substrate with respect to the transport system (180 to 200) and the mark-detecting operation effected by the mark detecting system (24a), during which the other stage (WS2 or WS1) performs the exposure operation effected by the projection optical system (PL). In such an arrangement, the operation corresponding to the time T1, the time T2, and the time T3 explained above can be performed by the one substrate stage, and the operation corresponding to the time T4 can be performed by the other substrate stage. Accordingly, it is possible to further improve the throughput.
In the projection exposure apparatus, at least one mark detecting system such as alignment system may be provided separately from the projection optical system. However, for example, when two mark detecting systems are provided separately from the projection optical system, it is also preferable, that the two mark detecting systems (24a, 24b) are arranged on both sides of the projection optical system (PL) along a predetermined direction; and the controller (90) is operated such that the reference mark on the first substrate stage (WS1) or the mark on the sensitive substrate (W1) held on the first substrate stage (WS1) is detected by using the one mark detecting system (24a), and the reference mark on the second substrate stage (WS2) or the mark on the sensitive substrate (W2) held on the second substrate stage (WS2) is detected by using the other mark detecting system (24b). In this embodiment as described above, the sensitive substrate on the one substrate stage may be exposed by using the projection optical system located at the center (exposure operation), during which the sensitive substrate on the other substrate stage may be subjected to the mark detection by using the one mark detecting system (alignment operation). When the exposure operation is changed to the mark detecting operation, then the one substrate stage having been located under the projection optical system can be easily moved to the position of the other mark detecting system, and the other substrate stage having been located at the position of the one mark detecting system can be easily moved to the position under the projection optical system, only by moving the two substrate stages along the predetermined direction toward the other mark detecting system. By doing so, it is possible to alternately use the two mark detecting systems.
According to the third aspect of the present invention, there is provided a projection exposure method for exposing a sensitive substrate (W1, W2) by projecting a pattern formed on a mask (R) through a projection optical system (PL) onto the sensitive substrates, characterized by:
preparing two substrate stages (WS1, WS2) each of which is movable independently on a two-dimensional plane while holding a sensitive substrate (W1, W2); and
performing, by using one stage (WS1 or WS2) of the two substrate stages (WS1, WS2), at least one of an exchange operation for the sensitive substrate and a detecting operation for a mark on the one stage or on the sensitive substrate held on the one stage, while executing an exposure operation for the sensitive substrate by using the other stage (WS2 or WS1) of the two substrate stages.
According to the projection exposure method, at least one of the operation corresponding to the time T1 and the operation corresponding to the time (T2+T3) explained above is performed on the one substrate stage, during which the operation corresponding to the time T4 is performed on the other substrate stage concurrently therewith. Accordingly, it is possible to improve the throughput as compared with the conventional sequential process which requires the time (T1+T2+T3+T4). Especially, when the operation corresponding to the time (T1+T2+T3) is performed by the one stage, during which the operation corresponding to the time T4 is performed by the other stage concurrently therewith, then it is possible to further improve the throughput.
In this aspect, the respective operations performed on the two substrate stage are not necessarily completed at the same time. However, it is also preferable that the operations of the two substrate stages are changed to one another at a point of time of completion of the operations of the two substrate stages. Accordingly, among the two stages, one stage, on which the operation is completed earlier, is subjected to a waiting mode, and the operations are changed to one another at the point of time of completion of the operation of the other stages. The waiting time may behave as a factor to lower the throughput. Therefore, it is desirable that the contents of the operations concurrently processed on the two substrate stages are divided so that the waiting time is decreased as short as possible.
According to the fourth aspect of the present invention, there is provided a method for exposing a sensitive substrate (W) by projecting a pattern formed on a mask (R) through a projection optical system (PL) onto the sensitive substrates, characterized by:
preparing two substrate stages (WS1, WS2) independently movable in the same plane while each holding a sensitive substrate (W);
exposing the sensitive substrate (W) held on-one of the two substrate stages (WS1 or WS2) with the pattern image of the mask (R) through the projection-optical system (PL);
measuring the positional relation between an alignment mark on the sensitive substrate (W) held on the other of the two substrate stages (WS2 or WS1) and a reference point on the other stage (WS2 or WS1) during exposure of the sensitive substrate (W) held on the one substrate stage (WS1 or WS2);
detecting the positional deviation of the reference point on the other substrate stage from a predetermined reference point in a projection area of the projection optical system and the coordinate position of the other substrate stage, with the reference point on the other substrate stage being positioned in the projection area, after completion of exposure of the sensitive substrate held on the one substrate stage; and
controlling the movement of the other substrate stage on the basis of the detected positional relation, the detected positional deviation and the detected coordinate position to perform alignment between the sensitive substrate held on the other stage and the pattern image of the mask.
According to the projection exposure method, while the sensitive substrate (W) held on the one substrate stage (WS1 or WS2) of the two substrate stages (WS1, WS2) is being exposed with the pattern image of the mask (R) through the projection optical system (PL), {circle around (1)} the positional relation between the alignment mark on the sensitive substrate (W) held on the other substrate stage (WS2 or WS1) of the two substrate stages and the reference point on the other stage (WS2 or WS1) is measured. As noted from this, the exposure action on the one substrate stage side and the alignment action on the other substrate stage side (measurement of the positional relation between the alignment mark on the sensitive substrate held on the other substrate stage and the reference point on the other substrate stage) can be performed in parallel. Thus, throughput can be improved in comparison with conventional technologies by which these actions were performed sequentially.
After exposure of the sensitive substrate held on the one substrate stage, {circle around (2)} the positional deviation of the reference point on the other substrate stage from the predetermined reference point in the projection area of the projection optical system (PL) and {circle around (3)} the coordinate position of the other substrate stage at the time of detecting the positional deviation are detected, with the reference point on the other substrate stage (WS2 or WS1) being positioned in the projection area. Then, the movement of the other substrate stage (WS2 or WS1) is controlled on the basis of the detected positional relation {circle around (1)}, the detected positional deviation {circle around (2)} and the detected coordinate position {circle around (3)} to perform alignment between the sensitive substrate held on the other stage and the pattern image of the mask.
Thus, it presents no disadvantages whether the interferometer (or coordinate system) for managing the position of the substrate stage at the time of detecting the positional relation {circle around (1)} between the predetermined reference point on the other substrate stage and the alignment mark on the sensitive substrate is the same as or different from the interferometer (or coordinate system) for managing the position of the stage during the detection of the positional deviation {circle around (2)} and during the detection of the coordinate position of the substrate stage {circle around (3)}. Regardless of whether these two interferometers are different, the alignment of the pattern image of the mask with the sensitive substrate placed on the other substrate stage can be performed highly accurately. This means that there is no need to successively measure the positions of the state by one interferometer during the alignment operation, the movement operation from an alignment position to the exposure position and the exposure operation.
Thus, when an off-axis alignment system (a detector for detecting an alignment mark is not directly below the projection optical system) is used as a mark detection system for detecting the alignment mark, for example, it becomes unnecessary to measure the positional relation between the predetermined reference point in the projection area of the projection optical system (the center of projection of the pattern image of the mask) and the center of detection of the alignment system, that is, unnecessary to measure the baseline amount. As a result, whatever distance exists between the projection optical system and the alignment system produces no disadvantage. Thus, the size of the substrate stage can be design irrespective of the baseline amount. Even if the substrate stage becomes small in size or light in weight, no disadvantage will emerge, and mark position measurement and pattern projection by exposure through the projection optical system can be carried out for the entire surface of the sensitive substrate, In this case, no influence of changes in the baseline amount is exerted.
According to the fifth aspect of the present invention, there is provided a projection exposure apparatus for exposing a sensitive substrate (W) by projecting a pattern through a projection optical system (PL) onto the sensitive substrates, comprising:
a first substrate stage (WS1), on which a reference mark is formed, moving in a two-dimensional plane while holding a sensitive substrate (W);
a second substrate stage (WS2), on which a reference mark is formed, moving in the same plane in which the first substrate stage (WS1) moves independently of the first substrate stage (WS1) while holding a sensitive substrate (W);
a mark detecting system (WA), provided apart from the projection optical system (PL), for detecting the reference mark on the substrate stage (WS1, WS2) or a mark on the sensitive substrate (W) held on the stage;
an interferometer system (26) for measuring the two-dimensional positions of the first substrate stage and the second substrate stage;
a moving device (201, 22) for moving each stage between a predetermined first position in a stage moving range during exposure during which the sensitive substrate held on the stage is exposed through the projection optical system, and a predetermined second position in a stage moving range during mark detecting during which the mark on the stage or the mark on the sensitive substrate held on the stage is detected by the mark detecting system; and
controller (28) for controlling the actions of the first substrate stage and the second substrate stage while monitoring the measured values of the interferometer system (26) so that during exposure of the sensitive substrate held on one of the first substrate stage and the second substrate stage, a mark detecting action by the mark detecting system (WA) is performed on the other of the first substrate stage and the second substrate stage, and then controlling the moving device (201, 22) to interchange the positions of the one substrate stage and the other substrate stage.
According to the above constitution, the controller (28) controls the actions of the two stages while monitoring the measured values of the interferometer system (26) so that during exposure of the sensitive substrate held on one stage of the two stages, a mark detecting action by the mark detecting system (for example, an alignment system) (WA) is performed on the other stage, and then controls the moving device(201, 221) to interchange the position of the one stage with the position of the other stage. This parallel execution of the exposure action on the one stage side and the alignment action on the other stage side enables throughput to be improved. Also, if the sensitive substrate is replaced on the substrate stage at the second position after interchange of the positions, actions of the two stages are interchanged, whereby during exposure of the sensitive substrate held on the other stage, a mark detecting action by the mark-detecting system (for example, the alignment system) (WA) can be performed on the one stage.
According to the projection exposure apparatus, the interferometer system (26) may has the first measuring axis (Xe) and the second measuring axis (Ye) intersecting each other perpendicularly at the center of projection of the projection optical system (PL), and the third measuring axis (Xa) and the fourth measuring axis (Ya) intersecting each other perpendicularly at the center of detection of the mark detecting system (WA). It is desirable that the controller (28) resets the measuring axes (Xe, Ye, Xa, Ya) of the interferometer system (26) in interchanging the positions of the one stage and the other stage. By means of constituting the interferometer system and the controller in this manner, since the interferometer system (26) has the first measuring axis (Xe) and the second measuring axis (Ye) intersecting each other perpendicularly at the center of projection of the projection optical system (PL), and the third measuring axis (Xa) and the fourth measuring axis (Ya) intersecting each other perpendicularly at the center of detection of the mark detecting system (alignment system) (WA), the positions of the substrate stages (WS1, WS2) can be managed precisely without Abbe""s error both during exposure of the sensitive substrate with the pattern through the projection optical system and during detection of the position detecting mark by the mark detecting system. Furthermore, the controller (28) resets the measuring axes (Xe, Ye, Xa, Ya) of the interferometer system (26) in interchanging the positions of the one stage and the other stage. During position interchange, the measuring axes of the interferometer system that has managed the positions of the substrate stages until then may be interrupted. Even in this case, it suffices to predetermine the positions at which to reset the measuring axes (Xe, Ye, Xa, Ya) of the interferometer system (26). After resetting, the positions of the first and second substrate stages can be managed using the measured values of the reset measuring axes.
According to the sixth aspect of the present invention, there is provided an exposure apparatus for exposing a sensitive substrates (W) by projecting a pattern on the sensitive substrate through a projection optical system (PL) comprising:
a first substrate stage (WS1), on which a reference mark is formed, for moving in a two-dimensional plane while holding a sensitive substrate (W);
a second substrate stage (WS2), on which a reference mark is formed, for moving in the same plane in which the first substrate stage (WS1) independently of the first substrate stage while holding a sensitive substrate (W);
a mark detecting system (WA) provided apart from the projection optical system (PL), for detecting the reference mark formed on the substrate stage or an alignment mark on the sensitive substrate held on the stage;
an interferometer system (26) for measuring the two-dimensional positions of the first substrate stage and the second substrate stage;
a moving device (201, 221) for moving each stage among three locations, i.e., a predetermined first position in a stage moving range during exposure during which the sensitive substrate (W) held on the stage is exposed through the projection optical system (PL), a predetermined second position in a stage moving range during alignment during which the mark on the stage or the mark on the sensitive substrate held on the stage is detected by the mark detecting system (WA), and a third position at which the sensitive substrate is passed on between the stage and an external substrate carrier mechanism; and
controller (28) for controlling the first and second substrate stages (WS1, WS2) and the moving device (201, 221) so that while the position of one of the first (WS1) and second (WS2) substrate stages is being managed by the interferometer system (26) and the sensitive substrate (W) held on the one stage is being exposed with the pattern through the projection optical system (PL), the replacement of the sensitive substrate (W), and an alignment action for measuring the positional relation between the alignment mark on the sensitive substrate (W) and a reference m ark on the other stage based on the results of detection by the mark detecting system (WA) and the measured values by the interferometer system (26) are sequentially performed on the other of the first and second substrate stages; and for controlling the two stages and the moving device so that after the actions on the two stages are both completed, the actions to be performed on the two stages are interchanged.
According to the exposure apparatus, the controller controls the two substrate stages (WS1, WS2) and the moving device (201, 221) so that while the position of the one substrate stage is being managed by the interferometer system and the sensitive substrate held on the one substrate stage is being exposed with the pattern through the projection optical system, the replacement of the sensitive substrate (W), and an alignment action for measuring the positional relation between the alignment mark on the sensitive substrate (W) after replacement and the reference mark on the other stage based on the detection results of the mark detecting system (WA) and the measured values by the interferometer system (26) are sequentially performed on the other substrate stage. Since the exposure action on the one substrate stage side and the replacement of the sensitive substrate as well as the alignment action on the other stage side are thus performed in parallel, throughput can be further improved. In this case, the sensitive substrate is replaced at the third position different from the first or second position. Since this position of replacement is different from the positions of the mark detecting system(for example, an alignment system) and the projection optical system, the disadvantage that the mark detecting system and the projection optical system impede the replacement of the sensitive substrate does not occur.
The controller also controls the two stages and the moving device so that after the actions of the two stages are both completed, the actions to be performed on the two stages are interchanged. Thus, after completion of the actions on the two stages, the sensitive substrate held on the other stage is exposed successively, and during this exposure, the mark detecting action by the mark detecting system (WA) can be performed on the one stage in parallel.
In this case, an electronic lens barrel, for example, may be used as the projection optical system, and the pattern may be directly drawn on the sensitive substrate with an electron beam. However, a mask (R) with the pattern formed thereon may be further provided, and the pattern image formed on the mask (R) via the projection optical system (PL) may be projected onto the sensitive substrates:(W) on the first substrate stage (WS1) and the second substrate stage (WS2).
In the exposure apparatus of the invention, it is desirable that the interferometer system (26) has a first measuring axis (Xe) and a second measuring axis (Ye) intersecting each other perpendicularly at the center of projection of the projection optical system (PL), and a third measuring axis (Xa) and a fourth measuring axis (Ya) intersecting each other perpendicularly at the center of detection of the mark detecting system (WA), and the controller (28) resets the first and second measuring axes (Xe and Ye) of the interferometer system (26) in moving each of the two stages (WS1, WS2) to the first position, and resets the third and fourth measuring axes (Xa and Ya) of the interferometer system (26) in moving each of the two stages (WS1, WS2) to the second position.
By means of constituting the interferometer and the controller, since the interferometer system (26) has the first measuring axis (Xe) and the second measuring axis (Ye) intersecting each other perpendicularly at the center of projection of the projection optical system (PL), and the third measuring axis (Xa) and the fourth measuring axis (Ya) intersecting each other perpendicularly at the center of detection of the mark detecting system (WA), the positions of the substrate,stages (WS1, WS2) can be managed precisely without Abbe""s error both during exposure of the sensitive substrate with the pattern through the projection optical system and during detection of the position detecting mark by the mark detecting system. Furthermore, the controller (28) resets the first and second measuring axes (Xe and Ye) of the interferometer system (26) in moving each of the two stages (WS1, WS2) to the first-position, and resets the third and fourth measuring axes (Xa and Ya) of the interferometer system (26) in moving each of the two stages (WS1, WS2) to the second position. Thus, prior to the start of exposure and the start of aligning measurement for each substrate stage, it is possible to rest the measuring axes that are required for the respective actions. Until then, the measuring axes of the interferometer system that has managed the positions of the respective substrate stages may be interrupted. After resetting, however, the positions of the two stages at the time of exposure and alignment can be managed using the measured values of the reset measuring axes.
In the exposure apparatus of the invention, it is desirable to further provide mark position detector (52A, 52B) for detecting the relative positional relation between the center of projection of the pattern image of the mask (R) formed by the projection optical system and the reference mark on the stage via the mask (R) and the projection optical system (PL). By so doing, the positional relation between the center of projection of the pattern image of the mask (R) and the reference mark on the substrate stage can be detected by the mark position detector (52A, 52B) via the mask (R) and the projection optical system (PL) when the substrate stages (WS1, WS2) are positioned at a position at which the positional relation between the predetermined reference mark on the substrate stage and the center of projection of the mask pattern image can be detected in the projection area of the projection optical system (PL). In this case, it is desirable that the position at which the positional relation between the predetermined reference mark on the substrate stage and the center of projection of the mask pattern image can be detected in the projection area of the projection-optical system (PL) be set as the first position, and the first and second measuring axes be reset at this position.
In the exposure apparatus, each of the substrate stages (WS1, WS2) may have a stage body (WS1a, Ws2a), and a substrate holding member (WS1b, WS2b) detachably mounted on the body (WS1a, WS2a) for holding the substrate, a reflecting surface for an interferometer may be provided on the side surface of the substrate holding member (WS1b, WS2b), and a reference mark (WM, RM) may be formed on the upper surface of the substrate holding member. When the exposure apparatus has such constitutions, the moving device (201, 221) may move the substrate holding member among the respective locations mentioned earlier instead of the substrate stage.
In the above cases, the moving device may be of any type which moves the substrate stage or the substrate holding member among the three locations, i.e., the first position, the second position and the third position (or between the first and second positions), without monitoring the measured values by the interferometer. For instance, the moving device may be composed of a robot arm (201, 221).
In the exposure apparatus, a fixed mirror serving as a reference for measurement by the interferometer may be located at any place. Fixed-mirrors (14X, 14Y; 18X, 18Y) serving as a reference for measurement by the interferometer may be attached to the projection-optical system (PL) and the mark detecting system (WA), respectively. In this case, compared with the fixed mirrors existing at other places, an error minimally occurs in the results of measurement under the influence of positional changes of the fixed mirrors over time or the influence of positional changes of the fixed mirrors associated with vibrations of the apparatus.
n the exposure apparatus, only two stages, the first substrate stage and the second substrate stage, are provided. However, at least one other substrate stage movable independently of the two substrate stages in the same plane as for these stages while holding a sensitive substrate may be further provided in addition to the first substrate stage (WS1) and the second substrate stage (WS2).
According to the seventh aspect of the present invention, there is provided a projection exposure apparatus for exposing a plurality of shot areas divided on a sensitive substrate (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto each of the shot areas, characterized by comprising:
a first substrate stage (WS1) which is movable on a two-dimensional plane while holding a sensitive substrate (W1);
a second substrate stage (WS2) which is movable independently from the first substrate stage (WS1) on the same plane as that for the first substrate stage (WS1) while holding
a sensitive substrate (W2);
a positional information detecting system (for example, 24a, . . . 130) for detecting the positional information of at least one shot area of the sensitive substrate (W1 or W2) held on the substrate stage (WS1 or WS2) provided apart from the projection optical system (PL);
substrate-driving systems (LS) provided for the first substrate stage (WS1) and the second substrate stage (WS2) respectively, for adjusting surface positions of the sensitive substrates (W1 or W2) held on the stages (WS1 or WS2); and
a controller (90) for controlling-the two stages (WS1, WS2) so that a positional information detecting operation based on the use of the positional information detecting system (24a, 130) is performed for one stage (for example, WS1) of the first substrate stage (WS1) and the second substrate stage (WS2), during which an exposure operation based on the use of the projection optical system (PL) is performed for the other of the stages (for example WS2), thereafter controlling one of the stages (WS1) so that the exposure operation based on the use of the projection optical system (PL) is performed for the one of the stages (WS1), and controlling the substrate-driving system (LS1) for the one of the stages (WS1) to perform an alignment of the shot area in exposure, using information on a surface position of the shot area resulted from the positional information detection.
According to the exposure apparatus, the two stages are controlled by the controller so that the detection of positional information based on the use of the positional information detecting system is performed for one of the stages of the first substrate stage and the second substrate stage, during which the exposure operation is performed by using the projection optical system for the other of the stages. Accordingly, the mark-measuring operation for the one of the stages is processed concurrently in parallel to the exposure operation for the other of the stages. Thus, it is possible to contemplate improvement in throughput as compared with the conventional technique in which these operations have been sequentially performed. Further, after completion of the concurrent process of the mark-measuring operation for one of the stages and the exposure operation for the other stage, the controller controls the one of the stages so that the exposure operation based on the use of the projection optical system is performed for the one of the stages, and the controller controls the substrate-driving system for the one of the stages on the basis of the detection result obtained by using information of the surface position of the shot area during the detection of the positional information for the one of the stages. Accordingly, during the exposure operation for the one of the stages, the substrate-driving system for the one of the stages is controlled using the surface position (Z-directional position) obtained during the detection of the positional information so that the surface position of the sensitive substrate can be quickly driven into a position near to the image formation plane of the projection optical system.
In the exposure apparatus, the positional information detecting system may comprise at least one alignment system (24a) for measuring a mark on the sensitive substrate held on the substrate stage and a first detecting system (130) for detecting positional information of a surface of the sensitive substrate during measurement operation of the mark-based on the use of the alignment system. Further, the positional information detecting system may be provided with a second detecting system (132) for detecting positional information of a surface of the sensitive substrate during exposure operation based on the use of the projection optical system. The controller (90) may control the two stages so that the detection by using the positional information detecting system for one of the stages of the first substrate stage and the second substrate stage is performed, during which the exposure operation based on the use of the projection optical system is performed for the other of the stages. After that, the controller may control the one of the stages so that the exposure operation based on the use of the projection optical system is performed for the one of the stages. And also, the controller may control the substrate-driving system (LS) for the one stage on the basis of the detection result obtained by using the first detecting system during the mark-measuring operation for the one stage and the detection result obtained by using the second detecting system during the exposure operation for the one stage to perform an alignment in the exposure of the shot area. The substrate-driving system can be further adjusted finely on the basis of the detection result obtained by using the second detecting system so that the surface of the sensitive substrate coincides with the image formation plane. Therefore, it is possible to perform quick and highly accurate focus/leveling control.
It is desirable that the projection exposure apparatus is a scanning type projection exposure apparatus (for example, a step-and-scan type exposure apparatus) for exposing sensitive substrates with an image of a pattern formed on a mask (R) by moving the sensitive substrate in a scanning direction with respect to an exposure area (IF) which is conjugate to an illumination area (IA) illuminated with an illumination light beam, in synchronization with movement of the mask in the scanning direction with respect to the illumination area. In this case, the controller (90) controls the two stages so that the detection by using the positional information detecting system for one stage of the first substrate stage and the second substrate stage is performed, during which the exposure operation based on the use of the projection optical system is performed for the other of the stages. After that, when the one stage is controlled so that the exposure operation based on the use of the projection optical system is performed for the one stage, upon exposure for shot areas in the vicinity of outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate with respect to the exposure area (IF), of a plurality of shot areas on the sensitive substrate held on the one of the stages, the controller may control the substrate-driving system (LS) on the basis of a detection result obtained by using the first detecting system (130) during detecting the positional information of the one stage (WS1) and a detection result obtained by using the second detecting system (132) during the exposure operation for the one stage. And, the controller may control the substrate-driving system (LS) for the one stage by using only the detection result obtained by using the second detecting system (132) upon exposure for the other shot areas than the shot areas in the vicinity of outer circumstance to perform an alignment in the exposure of the shot area. In this case, when the shot areas in the vicinity of the outer circumference, which are set to be subjected to scanning from the outside to the inside of the sensitive substrate, concerning the exposure area for which information on the surface position of the sensitive substrate during exposure for the previous shot is not obtained, are exposed during the exposure operation for the one stage, the substrate-driving system for the one stage can be controlled on the basis of the detection result obtained by using the first detecting system during the mark-measuring operation for the one stage to drive the surface position of the sensitive substrate into the position near to the image formation plane of the projection optical system. Further, the substrate-driving system can be further adjusted finely on the basis of the detection result obtained by using the second detecting system so that the surface of the sensitive substrate coincides with the image formation plane. On the contrary upon exposure for shot areas other than the above, for which information on the surface position of the sensitive substrate during exposure for the previous shot is obtained, the substrate-driving system for the one stage is controlled on the basis of the information on the surface position of the sensitive substrate during exposure for the previous shot prior to the start of exposure for the exposure-objective shot area so that the surface position of the sensitive substrate is quickly driven into the position near to the image formation plane of the projection optical system, followed by performing the adjustment for the surface position (xe2x80x9cfocus/levelingxe2x80x9d adjustment) of the sensitive substrate by using only the detection result obtained by using the second detecting system during exposure. Therefore, it is possible to perform quick and highly accurate focus/leveling control in any exposure of shot area.
According to the eighth aspect of the present invention, there is provided a projection exposure method for exposing sensitive substrates (W1 or W2) with an image of a pattern formed on a mask (R) via a projection optical system (PL), comprising the steps of:
preparing two substrate stages (WS1, WS2) which is movable independently on an identical two-dimensional plane while-each holding a sensitive substrate (W1 or W2);
measuring positional information of at least one shot area on the sensitive substrate (for example, W1) held on one stage (for example, WS1) of the two stages (WS1, WS2);
exposing the sensitive substrate (W2) held on the other stage (WS2) of the two stages (WS1, WS2) with the image of the pattern formed on the mask (R) during the period in which the measuring operation for the positional information is performed for the one of the stages (WS1); and
exposing the sensitive substrate held on the one of the stages (WS1), after completion of the exposure operation performed for the other of the stages (WS2), while adjusting a surface position of the sensitive substrate (W1) held on the one of the stages (WS1) on the basis of the measured positional information.
According to the exposing method, for example, in one stage, the mark-measuring operation for an alignment mark of sensitive substrate and detection of positional information such as the relative position with respect to the predetermined reference plane of the sensitive substrate are performed for one stage of the two stages, during which, in parallel thereto, the sensitive substrate held on the other stage of the two stages is exposed with the image of the pattern on the mask. Accordingly, owing to the concurrent and parallel process of the mark-measuring operation for the one stage and the exposure operation for the other stage, it is possible to contemplate improvement in throughput as compared with the conventional technique in which these operations have been performed in a. sequential manner. After completion of the exposure operation for the other stage, namely after completion of the concurrent operations on the two stages, the sensitive substrate held on the one stage is subjected to exposure. During the exposure, the surface position of the sensitive substrate held on the one stage is adjusted using information on the surface position of the shot area of the sensitive substrate held on the one stage detected previously, with respect to the predetermined reference plane. Accordingly, during the exposure operation effected for the one stage, the surface position of the sensitive substrate held on the one stage can be quickly driven into a position near to the image formation plane of the projection optical system on the basis of the information on the surface position previously detected. Therefore, it is possible to perform quick and highly accurate focus/leveling contral.
According,to the ninth aspect of the present invention, there is provided a projection exposure apparatus for exposing a sensitive substrate (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by comprising:
a first substrate stage (WS1) on which a reference mark is formed, for moving in a two-dimensional plane while holding a sensitive,substrate (W1);
a second substrate stage (WS2) on which a reference mark is formed, for moving in the same plane as for the first substrate stage (WS1) independently of the first substrate stage (WS1) while holding a sensitive substrate (W2);
at least one a mark detecting system (24a) provided apart from the projection optical system (PL), for detecting the reference mark on the substrate stage (WS1, WS2) or an alignment mark on the sensitive substrate (W1, W2) held on the substrate stage (WS1, WS2);
an interferometer system provided with a first length-measuring axis (BI1X) for measuring apposition of the first substrate stage (WS1) in a direction of a first axis from one side in the direction of the first axis passing through a projection center of the projection optical system (PL) and a detection center of the mark detecting system (24a), a second length-measuring axis (BI2X) for measuring a position of the second substrate stage (WS2) in the direction of the first axis from-the other side in the direction of the first axis, a third length-measuring axis (BI3Y) which perpendicularly intersects the first axis at the projection center of the projection optical system (PL), and a fourth length-measuring axis (BI4Y) which perpendicularly intersects the first axis at the detection center of the mark detecting system (24a), the interferometer system measuring two-dimensional positions of the first and second substrate stages (WS1 and WS2) respectively by using the length-measuring axes (BI1X to BI4Y).
According to the projection exposure apparatus, the sensitive substrates are held on the first and second substrate stages respectively to be independently movable on the two-dimensional plane. The mark detecting system such as an alignment system, which are provided apart from the projection optical system, are used to detect the reference mark on the substrate stage and/or the mark on the sensitive substrate held on the substrate stage. The two-dimensional positions of the first and second substrate stages are measured by using the system respectively. As for the length-measuring axes of the interferometer system, the first length-measuring axis and the second length-measuring axis are- provided on one side and the other side of the first and second substrate stages respectively along the direction of the first axis passing through the projection center of the projection optical system and the detection center of the mark detecting system. The first length-measuring axis is used to measure the position of the first substrate stage in the direction of the first axis, and the second length-measuring axis is used to measure the position of the second substrate stage in the direction of the first axis. The third length-measuring axis is provided so that it perpendicularly intersects the first axis at the projection center of the projection optical system. The fourth length-measuring axis is provided so that it perpendicularly intersects the first axis at the detection center of the mark detecting system. Accordingly, the reference marks formed on the two substrate stages can be detected by using the mark detecting system. During the mark detection, the two-dimensional position of the first substrate stage is measured by using the interferometers having the first length-measuring axis and the fourth length-measuring axis which mutually intersect perpendicularly at the detection center of the mark detecting system, and the two-dimensional position of the second substrate stage is measured by using the interferometers having the second length-measuring axis and the fourth length-measuring axis which mutually intersect perpendicularly at the detection center of the mark detecting system. Therefore, the position of any of the stages is accurately measured without any Abbe error.
On the other hand, during the exposure for the mask pattern effected by the projection optical system, the two-dimensional position of the first substrate stage is measured by using the interferometers having the first length-measuring axis and the third length-measuring axis which mutually intersect perpendicularly at the projection center of the projection optical system, and the two-dimensional position of the second substrate stage is measured by using the interferometers having the second length-measuring axis and the third length-measuring axis which mutually intersect perpendicularly at the projection center. Therefore, the position of any of the stages is accurately measured without any Abbe error. Especially, the first length-measuring axis and the second length-measuring axis are arranged in the positional relationship as described above. Accordingly, the length-measuring axis is not intercepted during the period in which the first substrate stage and the second substrate stage are moved in the direction of the first axis. Therefore, the two substrate stages can be moved and reciprocated between the mark detecting system and the projection optical system on the basis of the measured values obtained by using the interferometers having these length-measuring axes. For example, the second substrate stage can be located under the projection optical system during the period in which the first substrate stage is disposed under the mark detecting system. Accordingly, it is possible to concurrently process the exposure operation effected by the projection optical system and the position-detecting operation effected by the mark detecting system for the marks on the respective substrate stages or the marks on the sensitive substrates in parallel to one-another. As a result, it is possible to improve the throughput.
The projection exposure apparatus further may be provided with a controller (90) for controlling the first substrate stage and the second substrate stage (WS1, WS2), so that a position of one stage of the first substrate stage and the second substrate stage is managed based on the use of a measured value obtained by using the third length-measuring axis (BI3Y) of the interferometer system, while exposing the sensitive substrate on the one stage, during which a positional relationship between an alignment mark on the sensitive substrate held on the other stage and a reference mark (MK) on the other stage is obtained based on the use of a detection result obtained by using the mark detecting system and a measured value obtained by using the fourth length-measuring axis (BI4Y) of the interferometer system, and after exposing the one sensitive substrate, a position of the other stage is measured by using the third length-measuring axis (BI3Y), while a relative positional relationship between the reference mark on the other stage and a predetermined reference point within a projection area of the projection optical system is obtained.
The controller controls the operations of the two substrate stages as follows. That is, for example, the position of the first substrate stage is managed based on the use of the measured value obtainedby using the third length-measuring axis of the interferometer system. During the period in which the sensitive substrate held on the first substrate stage is exposed, the positional relationship between the alignment mark on the sensitive substrate held on the second substrate stage and the reference mark on the second substrate stage is detected by using the detection result obtained by the mark detecting system and the measured value by using the fourth length-measuring axis of the interferometer system. Further, the controller measures the position of the second substrate stage based on the use of the measured value obtained by using the third length-measuring axis, while controlling the second substrate stage so that it moves to a position at which a positional relationship between a reference mark on the second substrate stage and a predetermined reference point within a projection area of the projection optical system such as the projection center to obtain the positional relationship thereof That is, the controller is capable of controlling the operations of the two stages as follows. The position of the first stage is managed without any Abbe error with respect to the sensitive substrate held on the first stage, based on the use of the measured value obtained by using the third length-measuring axis at the projection center of the projection optical system, while the image of the pattern of the mask is projected through the aprbjection optical system, during which the positional relationship between the alignment mark on the sensitive substrate held on the second stage and the reference mark on the second stage is accurately detected without any Abbe error based on the use of the detection result obtained by using the mark detecting system and the measured value obtained by using the fourth length-measuring axis at the detection center of the mark detecting system. Accordingly, it is possible to concurrently perform the exposure operation effected on the first stage and the alignment operation effected on the second stage as described above. Thus, it is possible to improve the throughput.
In addition, when the operations of the both stages are completed, the controller measures a position of the second substrate stage based on the use of the measured value obtained by using the third length-measuring axis, while moving the second substrate stage to the position at which the positional relationship between the predetermined reference point within a projection area of the projection optical system and the reference mark on the second substrate stage is detectable so as to manage the position of the second substrate stage on the base of the reference mark. Accordingly, as for the second substrate stage for which the positional relationship between the reference mark on the second stage and the alignment mark on the sensitive substrate has been-measured (the alignment has been completed), its position can be managed based on the use of the measured value obtained by using the third length-measuring axis without any inconvenience, even when the fourth length-measuring axis used during the measurement of the alignment mark falls into an immeasurable state. Therefore, it is possible to detect the positional relationship between the reference mark on the second substrate stage and the predetermined reference point within the projection area of the projection optical system. Moreover, it is possible to perform the exposure while executing the positional adjustment for the projection area of the projection optical system and the sensitive substrate on the basis of the positional relationship, the measurement result of the alignment, and the measured value by using the third length-measuring axis. That is, the position of the second substrate stage can be managed during the exposure by using the another length-measuring axis, even when the measurement is impossible by using the length-measuring axis which has been used to manage the position of the second stage during the alignment. Further, it becomes unnecessary that the alignment operation of the first or the second substrate stages, the movement operation from the alignment position to the exposure position and the exposure operation are subsequently observed. Therefore, it is possible to miniaturize the reflective surface of the stage for reflecting the interferometer beam for each of the length-measuring axes. Thus, it is possible to miniaturize the substrate stage.
In the projection exposure apparatus, the mark detecting system may be an alignment system. Also, it is desirable that the interferometer of the third length-measuring axes is reset when the other stage is moved to a position at which the relative positional relationship between the reference mark on the other stage and the predetermined reference point within the projection area of the projection optical system. By means of resetting the interferometer of the third length-measuring axes at this time, the reference mark position on the other stage on the basis of the reference point within the projection area of the projection optical system and the position of the alignment mark of the sensitive substrate on the other stage is managed more easily.
The projection exposure apparatus further comprises another mark detecting system (24b) having a detection center on the first axis, disposed on a side opposite to the mark detecting system (24a) with respect to the projection optical system (PL), wherein the interferometer system further provided with a fifth length-measuring axis (BI5Y) which perpendicularly intersects the first axis at a detection center of the another mark detecting system (24b); and the controller (90) may control ;the first and the second stage as follows. The controller manages the position of the one substrate stage based on the use of the measured value obtained by the third length-measuring axis (BI3Y) of the interferometer system, while exposing the sensitive substrate held on the one stage during which the positional relationship between the alignment mark on the sensitive substrate held on the other stage and the reference mark on the other stage is obtained based on the use of the detection result obtained by using the mark detecting system and the measured value obtained by using the fourth length-measuring axis (BI4Y) of the interferometer system, and, after exposing the one stage, moving the one stage so that, the reference mark on the one stage is positioned within the another mark detecting system while the position of the one stage is measured based on the use of the measured value obtained by using the fifth length-measuring axis (BI5Y).
The controller is capable of controlling the operations of the two stages as follows. That is, the position of the first substrate stage is managed without any Abbe error with respect to the sensitive substrate held on the first substrate stage, based on the use of the measured value obtained by using the third length-measuring axis which perpendicularly intersects the length-measuring axes (the first length-measuring axis and the second length-measuring axis) in the first axis direction at the projection center of the projection optical system, while the image of the pattern formed on the mask is subjected to exposure through the projection optical system, during which the positional relationship between the alignment mark on the sensitive substrate held on the second substrate stage and the reference mark on the second substrate stage is accurately detected without any Abbe error based on the use of the detection result obtained by using the mark detecting system and the measured value obtained by using the fourth length-measuring axis which perpendicularly intersects the length-measuring axes (the first length-measuring axis and the second length-measuring axis) in the first axis direction at the detection center of the mark detecting system. Accordingly, it is possible to concurrently perform the exposure operation effected on the one substrate stage and the alignment operation effected on the second substrate stage as described above.
Then, the controller controls the operation of the first substrate stage as follows. That is, when the above-mentioned operations of the both stages are completed, the position of the first substrate stage is measured by the measured value obtained by using the fifth length-measuring axis, while obtaining the relative position between the detection center of another mark detecting system and the reference mark on the first substrate stage. Accordingly, as for the first substrate stage for which the exposure for the sensitive substrate has been completed, the position of the first substrate stage can be managed without any Abbe error, based on the use of the reference mark on the first substrate stage and the measured value obtained by using the fifth length-measuring axis. Further, there is no inconvenience, even when the third length-measuring axis used during the exposure falls into an immeasurable state. Therefore, the exposure operation effected on the first stage and the exposure operation effected on the second stage can be easily changed by sifting the two substrate stages in the first axis direction, thereby, the measurement of the position of the second substrate stage, for which the alignment operation has been completed, is enabled based on the use of the measured value obtained by the third length-measuring axis, and the measurement of the position of the first substrate stage, for which the exposure operation has been completed, is enabled based on the use of the measured value obtained by the fifth length-measuring axis.
In this aspect, the projection exposure apparatus may further comprises a transport system (180 to 200) for receiving and transmitting the sensitive substrate (W1, W2) between the first substrate stage (WS1) and the second substrate stage (WS2), and it is desirable that the controller controls the one stage so as to position the reference mark thereon within the detection area of the another mark detecting system (24b), and at the position, the substrate is received and transmitted between the one stage and the transport system (180 to 200). In this constitution, in addition to the change between the exposure operation and the alignment operation described above, the controller allows the substrate to be received and transmitted between the first substrate stage and the transport system in the state in which the reference mark on the one stage is positioned within the detection area of the another mark detecting system using the fifth length-measuring axis of the interferometer system. Accordingly, the measurement of the position of the reference mark as the operation to start the alignment and the change of the sensitive substrate can be performed in a stationary state of the substrate stage. In addition to the,fact that the movement time required for the substrate stage to move from the wafer exchange position to the alignment start position is zero, it is possible to perform the operations concerning the time T1, the time T2, and the time T3, for example on the side of the first substrate stage, while it is possible to perform the operation concerning the time T4 on the side of the second substrate stage. Therefore, it is possible to further improve the throughput.
In the projection exposure apparatus of the invention, the predetermined reference point within the projection area of the projection optical system (PL) may be the projection center for the image of the pattern formed on the mask (R); and the projection exposure apparatus further may comprise a mark position-detector (142, 144) for detecting a relative positional relationship between the projection center for the image of the pattern formed on the mask (R) and reference marks (MK1, MK2, MK3) on the stage, via the mask (R) and the projection optical system. The mark position-detector may be a detector detecting the marks through the projection optical system, such as a reticle alignment microscope.
In the projection exposure apparatus, as for the mark detecting system, at least one or more mark detecting systems may be provided apart from the projection optical system. However, it is also preferable that the two mark detecting systems (24a, 24b) are disposed on one side and the other side (each side) of the projection optical system (PL) in the direction of the first axis. When the mark detecting systems are arranged in the positional relationship as described above, then the sensitive substrate on the one substrate stage may be exposed by using the projection optical system located at the center (exposure operation), during which the sensitive substrate on the other substrate stage may be subjected to the mark detection by using any of the mark detecting systems (alignment operation). When the exposure operation is changed 143 to the alignment operation, then the substrate stage for which the alignment operation has been completed can be moved to the position under the projection optical system and the other substrate stage can be moved to the position of the mark detecting system, only by deviating the two substrate stages in the direction of the first axis.
In the projection exposure, it is also preferable that the projection exposure apparatus further comprises a controller (90) for independently controlling movement of the first and second substrate stages on the basis of a result of measurement performed by the interferometer system (for example, the length-measuring axes BI1X to BI4Y) so that each of the first and second substrate stages (WS1 and WS2) is capable of performing an exposure operation-effected by the projection optical system (PL) and a mark-detecting operation effected by the mark detecting system (for example, 24a). The controller independently controls the movement of the first and second substrate stages on the basis of the result of measurement performed by the interferometer system (for example, the length-measuring axes BI1X to B14Y) so that each of the first and second substrate stages is capable of performing the exposure operation effected by the projection optical system (PL) and the mark-detecting operation effected by the mark detecting system (for example, 24a), and hence the exposure operation effected by the projection optical system and the mark-detecting operation effected-by the mark detecting system can be reliably performed for the sensitive substrate disposed on any of the substrate stages.
In this arrangement, if the spacing distance between the length-measuring axes BI3Y and BI4Y is too large, the length-measuring axes BI3Y, BI4Y are deviated from the substrate stage when the first substrate stage and the second substrate stage are moved. On the other hand, if such a situation is avoided, the interference between the both stages might occur. Therefore, in order to present such inconveniences, it is desirable that the controller (90) changes the third length-measuring axis (BI3Y) and the fourth length-measuring axis (BI4Y) of the interferometer system (for example, the length-measuring axes BI1X to BI4Y) between detection of the mark effected by the mark detecting system (for example, 24a) and exposure effected by the projection optical system (PL) for the first and second substrate stages (WS1 and WS2) respectively so that no inconvenience occurs even when the substrate stage is deviated from the length-measuring axis. In the constitution as described above, the spacing distance between the third length-measuring axis (BI3Y) and the fourth length-measuring axis (BI4Y) can be widened to avoid the interference between the both stages. Further, when the length-measuring axis BI3Y, BI4Y is deviated from the substrate stages during the movement of the first substrate stage and the second substrate stage, the controler can be used to change the length-measuring axis so that the two-dimensional position of each of the substrate stages is accurately measured at each of the processing positions by using the interferometer system.
According to the tenth aspect of the present invention, there is provided a method for exposing sensitive substrates by projecting an image of a pattern on a mask (R) via a projection optical system onto the sensitive substrates, characterized by:
using two substrate stages (WS1, WS2) each of which is movable independently on an identical plane while each holding a sensitive substrate (W1, W2);
measuring a position of one stage of the two stages by using a first interferometer, while exposing the sensitive substrate (W1, W2) held on the one stage,
measuring the position of the other stage by using a second interferometer during exposure for the substrate held on the one stage, while measuring a positional relationship between an alignment mark on the substrate held on the other stage and a reference mark on the other stage,
moving the other stage to a position at which a positional relationship between the reference mark on the other stage and a predetermined reference point within a projection area of the projection optical system is obtained, after completion of the exposure for the substrate on the one stage; and
performing alignment for the sensitive substrate held on the other stage and the image of the pattern on the mask, by using the first interferometer, on the basis of the relationship between the alignment mark on the substrate held on the other stage and the reference mark on the other stage, and a relationship between the reference mark on the other stage and the predetermined reference point within the projection area of the projection optical system.
According to the projection exposure method, for example, the exposure operation for the sensitive substrate held on the first substrate stage, and the measurement of the positional relationship (alignment operation) between the positional alignment mark of the sensitive substrate held on the second substrate stage and the reference mark on the stage are performed concurrently in parallel to one another. During this process, the position of the first substrate stage is managed by the aid of the first interferometer, and the position of the second stage is managed by the aid of the second interferometer. When the exposure operation effected on the side of the first substrate stage is completed, the position of the second stage is measurable by using the first interferometer which has been used to manage the position of the first substrate stage, and also, the second substrate stage is moved to the position at which the relative-position between the predetermined reference point within the projection area of the projection optical system and the reference mark on the second substrate stage is detectable. Subsequently, the positional adjustment is performed for the sensitive substrate held on the second stage and the image of the pattern formed on the mask by using the first interferometer, on the basis of the positional relationship between the reference mark on the second stage and the positional alignment mark on the sensitive substrate held on the second stage measured previously. Thus, the sensitive substrate is exposed by projection with the image of the pattern formed on the mask.
That is, the exposure operation for the sensitive substrate held on the one substrate stage, and the alignment operation for the sensitive substrate held on the second stage are concurrently performed in parallel to one another. After that, the first substrate stage is retracted to a predetermined substrate exchange position, concurrently with which the second substrate stage is moved toward the position on which the position of the reference mark of the second substrate stage is detectable with respect to the predetermined reference point (for example, the projection center of the image of the pattern formed on the mask) within the projection area of the projection optical system, and then the positional relationship between the both is detected. Further, the alignment is performed for the sensitive substrate held on the second substrate stage and the image of the pattern formed on the mask on the basis of the obtained detection result and the positional relationship between the alignment mark and the reference mark on the stage previously measured during the alignment operation, while the position of the second stage is managed by using the first interferometer.
Therefore, it is possible to improve the throughput by concurrently perform the exposure operation for the sensitive substrate on the first substrate stage and the alignment operation for the sensitive substrate on the second substrate stage. Even when the second interferometer, which has been used to manage the position of the other stage during the alignment, cannot be used for the measurement, the measurement based on the use of the first interferometer makes it possible to manage the position of the second substrate stage during the exposure. Thus, it becomes unnecessary that the stage position is observed continuously by means of one measuring axis or one interferometer through the alignment operation, the movement operation from the alignment position to the exposure position and exposure operation. Therefore, it is possible to miniaturize the reflective surface of the stage for reflecting the interferometer beam of each of the interferometers, and thereby it is possible to miniaturize the substrate stage.
According to the eleventh aspect of the present invention, there is provided a projection exposure apparatus for exposing a sensitive substrate (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by comprising:
a first substrate stage (WS1) which is movable on a two-dimensional plane while holding a sensitive substrate (W1);
a second substrate stage (WS2) which is movable independently from the first substrate stage (WS1) on the same plane as that for the first substrate stage (WS1) while holding a sensitive substrate (W2);
a transport system (180 to 200) for delivering the sensitive substrate with respect to the first and second substrate stages (WS1, WS2); and
a controller (90) for controlling operations of the both stages so that one stage of the first (WS1) and second (WS2) substrate stages performs delivery of the sensitive substrate with respect to the transport system (180 to 200), during which the other stage performs an exposure operation.
According to the projection exposure apparatus, the controller controls the operations-of the both stages so that one stage of the first substrate stage and the second substrate stage performs the delivery of the sensitive substrate with respect to the transport system, during which the other stage performs the exposure operation. Therefore, the operation corresponding to the time T1 explained above can be processed concurrently with the operation corresponding to the time T4. Thus, it is possible to improve the throughput as compared with the conventional sequential process which requires the time (T1+T2+T3+T4).
It is sufficient for any of the projection exposure apparatus that the exposure is performed by using one sheet of mask. However, it is also preferable that the projection exposure apparatus further comprises a mask stage (RST) which is capable of simultaneously carrying a plurality of masks (R); and a driving system (30) for driving the mask stage (RST) so that any of the masks (R) is selectively set at an exposure position. According to this embodiment, for example, in order to improve the resolving power, even when the so-called double exposure method is used to change the two masks so that overlay exposure is performed under an exposure condition-appropriate for each exposure area, then the double exposure can be performed in a continuous manner by using the two masks on the side of the one substrate stage, during which another operation such as alignment can be performed on the side of the other substrate stage concurrently therewith, only by allowing the two masks to be carried on the mask stage beforehand, and changing the masks and setting the mask stage at the exposure which would be otherwise resulted from the double exposure method, can be greatly improved.
As compared with the stationary type projection exposure apparatus such as the stepper for exposing the sensitive substrate by projection with the pattern formed on the mask via the projection optical system in a state in which the mask and the sensitive substrate are allowed to stand still, any of the above-mentioned projection exposure apparatus is more effective when the projection exposure apparatus is constructed as a scanning type projection exposure apparatus in which the mask (R) is carried on the mask stage (RST) which is movable in a predetermined direction, wherein the projection exposure apparatus further comprises a stage controller (38) for exposing the sensitive substrate (WS1, WS2) by projection with the pattern formed on the mask, while synchronously moving the mask stage (RST) with respect to any one of the first and second substrate stages (WS1 and WS2),because of the following reason. That is, it is possible to realize highly accurate exposure owing to the averaging effect on the image of the mask pattern in the projection area formed by the projection optical system, and it is possible to make exposure for a larger area by using the smaller projection optical system as compared with those used for the stationary type projection exposure apparatus.
According to the twelfth aspect of the present invention, there is provided a projection exposure apparatus for exposing sensitive substrates (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by having:
a first substrate stage (WS1) which is movable on a two-dimensional plane while holding a sensitive substrate (W1);
a second substrate stage (WS2) which is movable independently from the first substrate stage (WS1) on the same plane as that for the first substrate stage (WS1) while holding a sensitive substrate (W2);
an interferometer system (for example, a length-measuring axes BI1X to BI4Y) for measuring two-dimensional positions of the first substrate stage and the second substrate stage (WS1, WS2) respectively;
a storing device (91) which stores an interference condition for the interferometer system (for example, the length-measuring axes BI1X to BI4Y) to be used when the first substrate stage and the second substrate stage cause interference with each other; and
a controller (90) for controlling movement of the both stages (WS1, WS2) to cause no interference with each other while monitoring a measured value -obtained bye the interferometer system (for example, the length-measuring axes BI1X to BI4Y) on the basis of the interference condition stored in the storing device (91).
According to the projection exposure apparatus, the interferometer system is used to measure the two-dimensional positions of the first substrate stage and the second substrate stage which are independently movable on the two-dimensional plane while holding the sensitive substrates respectively, and the movement of the both stages is controlled by the controller to cause no interference while monitoring the measured value obtained by using the interferometer system, on the basis of the interference condition stored in the storing apparatus under which the first substrate stage and the second substrate stage cause interference with each other. Therefore, even when the two stages are independently moved to concurrently process the two operations in parallel to one another, it is possible to prevent the two stages from contact (interference).
The projection exposure apparatus may further comprises an alignment system provided apart from the projection optical system (PL), for detecting a reference mark on the substrate stage (WS1, WS2) or a mark on the sensitive substrate (W1, W2) held on the substrate stage (WS1, WS2); and a transport system (180 to 200) for delivering the sensitive substrate (W1, W2) with respect to the first substrate stage and the second substrate stage (WS1, WS2). The controller (90) may control the two substrate stages (WS1, WS2) so that one stage of the substrate stages (WS1 or WS2) performs at least one operation of a mark-detecting operation performed by the alignment system and a sensitive substrate (W1, W2)-delivering operation with respect to the transport system (180 to 200), while a measured value obtained by using the interferometer system (for example, length-measuring axes BI1X to BI4Y) is monitored, on the basis of the interference condition, during which the other stage (WS2 or WS1) is subjected to an exposure operation performed by using the projection optical system (PL), and when the controller (90) may control such that when the both stages (WS1, WS2) come to positions to cause interference with each other, the stage (WS1 or WS2) of the both""stages (WS1, WS2), which takes a longer time until completion of the operation, is preferentially moved until the both stages (WS1, WS2) are in a positional relationship of no interference, during which the stage (WS2 or WS1), which takes a shorter time until completion of the operation, is allowed to wait.
According to this constitution, the controller controls the both substrate stages so that the one stage of the substrate stages performs at least one of the operations of the sensitive substrate-delivering operation and the mark-detecting operation, while monitoring the measured value obtained by using the interferometer system, on the basis of the interference condition, during which the other substrate stage is subjected to the exposure operation, while the controller performs control such that when the both stages come to the positions to cause interference with each other, the stage, which takes a longer time until completion of the operation concerning the both stages, is preferentially moved until the both stages are in the positional relationship of no interference, during which the stage, which takes a shorter time until completion of the operation, is allowed to wait. Therefore, even when a situation of interference occurs during the concurrent process for the two operations while independently moving the two stages, the interference of the two stages can be avoided without decreasing the throughput by comparing the time until completion of the operation for the both stages, preferentially moving the one stage, and allowing the other stage to wait.
According to the thirteenth aspect of the present invention, there is provided a projection exposure apparatus for exposing sensitive substrates (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by comprising:
a first substrate stage (WS1), on which a reference mark is formed, moving on a two-dimensional plane while holding a sensitive substrate (W1);
a second substrate stage (WS2), on which a reference mark is formed, for moving independently from the first substrate stage (WS1) on the same plane as that for the first substrate stage (WS1) while holding a sensitive substrate (W2);
an alignment system (for example, 24a) provided apart from the projection optical system (PL), for detecting the reference mark on the substrate stage (WS1 or WS2) or a mark on the sensitive substrate (W1 or W2) held on the substrate stage (WS1 or WS2); and
a controller (90) for controlling the two stages (WS1, WS2) so that a mark-detecting operation is performed by the alignment system (for example, 24a) for the sensitive substrate held on one stage (WS1 or WS2) of the first substrate stage (WS1) and the second substrate stage (WS2), concurrently with which an exposure operation is performed for the sensitive substrate held on the other stage (WS2 or WS1), while an operation, which is included in the mark-detecting operation to be performed on the one stage (WS1 or WS2) and which affects the other stage (WS2 or WS1), is performed in synchronization with an operation which is included in the exposure operation to be performed on the other stage (WS2 or WS1) and which affects the one stage (WS1 or WS2), and for controlling the operations of the two substrate stages (WS1, WS2) so that operations, which are included in the respective operations to be performed on the first substrate stage (WS1) and the second substrate stage (WS2) and which make no influence with each other, are performed in synchronization with each other.
In the projection exposure apparatus, the controller controls the two stages so that the operation, which is included in the mark-detecting operation operated on the one stage and which affects the other stage (disturbance factor), is performed in synchronization with the operation which is included in the exposure operation operated on the other stage and which affects the one stage. (disturbance factor). Accordingly, the operations, which make influence with each other, are synchronized. Therefore, no trouble-occurs in the operations performed on the respective stages. Further, the controller controls so that the operations, which are included in the respective operations to be performed by the both stages and which make no influence with each other (non-disturbance factor), are performed in a synchronized manner. Therefore, no trouble occurs also in this case in the operations performed on the respective stages. Therefore, the position-detecting operation performed by the alignment system for the marks on the respective substrate stages or on the sensitive substrates can be concurrently processed in parallel to the exposure operation performed by the projection optical system. Consequently, it is possible to improved the throughput. Further, it is possible to concurrently process the two operations in an appropriate manner, because the operations performed on the two substrate stages make no influence with each other.
In this aspect, various combinations may be conceived for the operations which make no influence with each other. However, it is preferable that the one stage (WS1 or WS2) is stationary rested to measure the mark on the one stage (WS1 or WS2) or the mark on the sensitive substrate (W1 or W2) held on the one stage (WS1 or WS2) during a period for exposing, by projection, the sensitive substrate (W2 or W1) held on the other substrate stage (WS2 or WS1) with the image of the pattern formed on the mask (R). These operations do not make any influence with each other. Accordingly, it is possible to concurrently process, without any trouble, the highly accurate mark-detecting operation and the exposure operation.
On the other hand, various combinations may be conceived for the operations which make influence with each other. However, it is preferable that the one substrate stage (WS1 or WS2) is moved for detecting the next mark in synchronization with movement of the other substrate stage (WS2 or WS1) for the next exposure.
In this embodiment, it is preferable that the projection exposure apparatus further comprises a mask stage (RST) which is movable in a predetermined direction while carrying the mask (R), and a scanning system (for example, 38) for synchronously scanning the mask stage (RST) and the first substrate stage (WS1) or the second substrate stage (WS2) with respect to the projection optical system (PL), wherein the controller (90) stationary rests the one stage. (WS1 or WS2) to measure the mark on the one stage (WS1 or WS2) or the mark on the sensitive substrate (W1 or W2) held on the one stage (WS1 or WS2) during movement of the other substrate stage (WS2 or WS1) at a constant velocity in synchronization with the mask stage (RST). Accordingly, the scanning system is operated to move the mask stage and the other substrate stage at the constant velocity in a synchronized manner during the exposure. Therefore, the one stage is not affected thereby, for which the measurement of the mark is performed. The mark is measured in a stationary state which does not affect the other stage during the exposure, on the one stage for which the mark measurement is performed, during the movement of the other stage at the constant velocity (during the exposure). Accordingly, even during the process of the scanning exposure, the exposure operation and the mark-detecting operation can be concurrently dealt with in parallel to one another without any trouble by using the two stages.
In this embodiment, it is more desirable that the projection exposure apparatus further comprises a transport system (180 to 200) for delivering the sensitive substrate (W1 or W2) with respect to the first substrate stage and the second substrate stage (WS1, WS2) respectively, wherein the controller (90) controls operations of the two substrate stages (WS1, WS2) so that the one substrate stage (WS1 or WS2) performs at least one of the mark-detecting operation and a sensitive substrate (W1 or W2) delivering operation with respect to the transport system (180 to 200), concurrently with which the exposure operation is performed for the sensitive substrate (WS2 or WS1) held on the other stage, while an operation, which is included in the delivering operation and the mark-detecting operation to be performed on the one substrate stage (WS1 or WS2) and which affects the other stage (WS2 or WS1), is performed in synchronization with the operation which is included in the exposure operation to be performed on the other stage (WS2 or WS1) and which affects the one stage (WS1 or WS2), and the controller (90) controls the operations of the two substrate stages (WS1, WS2) so that the operations, which are included in the respective operations to be performed on the first substrate stage and the second substrate stage (WS1, WS2) and which make no influence with each other, are performed in synchronization with each other. According to this embodiment, the operations corresponding to the time T1, the time T2, and the time T3 explained above can be performed on the side of the one stage, while the operation corresponding to the time T4 can be performed on the side of the other stage. Therefore, the throughput is further improved, and it is possible to concurrently process the operations on the two stages respectively without any trouble.
In the projection exposure apparatus, the alignment system may be provided separately from the projection optical system. However, when the apparatus comprises, for example, two alignment systems separately from the projection optical system, it is preferable that the alignment systems (24a, 24b) are arranged on both sides of the projection optical system (PL) in a predetermined direction; and the controller (90) changes the operations of the both stages (WS1, WS2) when the operations of the both of the first substrate stage and the second substrate stage (WS1, WS2) are completed.
In the case of the above constitution, the projection optical system disposed at the central position is used to expose the sensitive substrate held on the one substrate stage (exposure operation ), while the one alignment system is used to detect the mark for the sensitive substrate held on the other substrate stage (alignment operation). When the exposure operation is changed to the alignment operation, only the movement of the two substrate stages toward the other alignment system along the predetermined direction makes it possible to move the one substrate stage having been located under the projection optical system to the position for the other alignment system, and move the other substrate stage having been located at the position for the one alignment system to the position under the projection optical system with ease. Thus, the two alignment systems can be alternately used as described above without any trouble.
According to the fourteenth aspect of the present invention, there is provided a projection exposure method for exposing sensitive substrates (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by comprising:
preparing two substrate stages, each of which moves independently on a two-dimensional plane while holding a sensitive substrate (W1, W2),each stage having a reference mark formed thereon; and
exposing, by projection, the sensitive substrate (W1 or W2) held on one of the stages (WS1 or WS2) with the image of the pattern formed on the mask, while stationary resting the other stage (WS2 or WS1) to detect the reference mark on the other stage (WS2 or WS1) or a mark on the sensitive substrate (W1 or W2) held on the other stage (WS2 or WS1).
According to the projection exposure apparatus, the other stage is stationary rested during the projection exposure with the image of the pattern formed on the mask for the sensitive substrate held on the one stage of the two substrate stages to detect the reference mark on the other stage or the alignment mark on the sensitive substrate held on the other stage. Therefore, the two stages are used such that the projection exposure operation is performed on the one stage, during which the mark-detecting operation is performed on the other stage in the stationary state. Therefore, the highly accurate exposure operation and the mark-detecting operation are concurrently dealt with in parallel to one another without being affected by the operation performed on the one stage or the other stage with each other. Thus, it is possible to improve the throughput.
According to the fifteenth aspect of the present invention, there is provided a projection exposure method for exposing sensitive substrates (W1, W2) by projecting an image of a pattern formed on a mask (R) via a projection optical system (PL) onto the sensitive substrates, characterized by comprising:
preparing two substrate stages, each of which moves independently on a two-dimensional plane while holding a sensitive substrate (W1, W2), each stage having a reference mark formed thereon; and
successively exposing, by projection, a plurality of portions on the sensitive substrate (W1, W2) held on one stage (WS1 or WS2) of the two substrate stages (WS1, WS2) with the image of the pattern formed on the mask (R), and successively detecting a plurality of marks on the sensitive substrate (W1, W2) held on the other stage (WS2 or WS1) concurrently therewith, while determining an order of the detection of the marks on the sensitive substrate (W1, W2) held on the other stage (WS2 or WS1) so that the two substrate stages (WS1, WS2) cause no interference with each other.
According to the present invention, the projection exposure is successively performed with the image of the pattern formed on the mask for the plurality of portions on the sensitive substrate held on the one stage of the two substrate stages which are independently movable on the two dimensional plane while holding the sensitive substrates respectively, concurrently with which the plurality of marks on the sensitive substrate held on the other stage are successively detected. During this process, the order of the detection of the marks on the sensitive substrate held on the other stage is determined so that the two substrate stages cause no interference with each other. Therefore, the order of the detection of the marks is determined in conformity with the movement of the stage which is subjected to the successive projection exposure process. Accordingly, the two stages are prevented from interference with each other, and the throughput can be improved by concurrently processing the operations.
According to the sixteenth aspect of the present invention, there is provided a scanning type projection exposure apparatus for exposing a sensitive substrate (W) with an image of a pattern formed on a mask (R) by moving the sensitive substrate (W) in a scanning direction with respect to an exposure area (IF) which is conjugate to an illumination area (IA) illuminated with an illumination light beam (EL), in synchronization with movement of the mask (R) in the scanning direction with respect to the illumination area (IA), the projection exposure apparatus comprising:
a substrate stage (WS) which is movable on a two-dimensional plane while holding the sensitive substrate (W);
a position-detecting system (151, 161) including detecting areas having a width, in a non-scanning direction perpendicular to a scanning direction, which is wider than that of an exposure area (IF), on one side and the other side in the scanning direction with respect to the exposure area (IF), for detecting a relative position of a surface of the sensitive substrate (W) with respect to a predetermined reference plane at least at one of a plurality of detecting points (for example, FA1 to FA9) set in the respective detecting areas along the non-scanning direction;
a substrate-driving system (LS) provided on the substrate stage (WS), which adjusts a surface position of the sensitive substrate (W) held on the stage (WS); and
a controller (90) which controls the substrate-driving system (LS) on the basis of detection result obtained by using the position-detecting system (151, 161), upon exposure for the sensitive substrate (W) held on the substrate stage (WS).
According to the projection exposure apparatus, the position-detecting system is arranged on each side in the scanning direction with respect to the exposure area, in the non-scanning direction perpendicular to the scanning direction respectively, having the detecting area with the width in the non-scanning direction wider than the exposure area. The relative position of the surface of the sensitive substrate with respect to the predetermined reference plane is detected at least at one of the plurality of detecting points set in the respective detecting areas along the non-scanning direction. The controller controls the substrate-driving system on the basis of the detection results obtained by using the position-detecting systems, upon exposure for the sensitive substrate held on the substrate stage. Accordingly, for example, unlike the conventional pre-measurement sensor merely including the detecting area having the same width as the exposure area in which it has been difficult to perform pre-measurement control in the area in the vicinity of the outer circumference of the sensitive substrate when the scanning is performed from the outside to the inside of the sensitive substrate, it is possible to detect the relative position of the surface of the adjacent portion of the sensitive substrate with respect to the predetermined reference plane, owing to the detecting points of the part of the detecting area protruding to the outside of the exposure area even in such a case. It is possible to adjust the surface position of the sensitive substrate by controlling-the substrate-driving system on the. basis of the detection data. Therefore, it is possible to avoid decrease in throughput which would be otherwise caused by the change in scanning direction for the sensitive substrate. It is possible to drive the focus control by utilizing the detection data.
Alternatively, during the exposure for a certain shot area existing at the outer circumference portion of the. substrate, the information on the surface position of a shot area adjacent thereto is detected by using the detecting points at the portions of the detecting area disposed on one side and the other side in the scanning direction protruding over the outside of the exposure area, and an obtained result is stored. By doing so, when the adjacent shot area is exposed, even if the adjacent shot is a shot area for which it is difficult to perform pre-measurement control by using the conventional pre-measurement sensor described above, it is possible to quickly drive the focus on the basis of the stored information on the surface position.
In this aspect, it is preferable that the controller (90) controls the substrate-driving system (LS) on the basis of at least one detection result for the plurality of detecting points (for example, FA1 to FA9) in the detecting area set on a front side of the exposure area in relation to the scanning direction for the sensitive substrate, of the detection results obtained by using the position-detecting systems. That is, the position-detecting system may be used as only a pre-measurement sensor.
Alternatively, various opportunities can be considered as timings to start control of the substrate-driving system in order to adjust the surface position of the sensitive substrate. However, it is preferable that when shot areas (212) in the vicinity of outer-circumference of the sensitive substrate (W) are subjected scanning exposure from the outside to the inside of the sensitive substrate (W), the controller (90) starts control for the substrate-driving system (LS) for adjusting the surface position of the sensitive substrate (W) on the basis of a detection result for a detecting point (FAA1 to FA9) which overlaps the sensitive substrate (W), from a point of time at which at least one of the plurality of detecting points (for example, FA1 to FA9) overlaps an effective area on the sensitive substrate (W), because of the following reason. That is, it is possible to quickly move the surface into a desired position (focus onto the surface) by starting the control of the substrate-driving system from the state in which at least one of the detecting points overlaps the effective area.
Alternatively, when one detecting point-overlaps the shot area, the surface position (including the inclination) of the sensitive substrate is adjusted as follows by the aid of the substrate-driving system. That is, it is preferable that when shot areas (212) in the vicinity of outer circumference of the sensitive substrate (W) are subjected scanning exposure, if only one detecting point (for example, FA3 to FA7) overlaps the shot area (212), then the controller (90) adjusts an inclination of the sensitive substrate (W) by the aid of the substrate-driving system (LS) on the basis of a predetermined fixed value. The predetermined fixed value is exemplified by an inclination of zero. In this case, the surface of the sensitive substrate is set on a horizontal plane including the surface position in the direction perpendicular to the reference plane detected by using the detecting points. Therefore, even when only one detecting point is used, it is possible to perform the leveling control in addition to the focus control.
Alternatively, it is preferable that when shot areas (212) in the vicinity of outer circumference of the sensitive substrate (W) are subjected scanning exposure, if only one detecting point (for example, FA3 to FA7) overlaps the shot area (212), then the controller (90) adjusts an inclination of the sensitive substrate (W) by the aid of the substrate-driving system (LS) on the basis of a detection result for the only one detecting point and a detection result for another detecting point (for example, FA1, FA2, FA8, FA9) which overlaps a shot area adjacent to the shot area (212) overlapped by the one detecting point. As described above, even when one detecting point in the exposure shot area is used, it is possible to perform the focus/leveling control with relative accuracy, by using the detection result for the adjacent shot area and the detection result for the one point. Further, it may be previously determined that a detection result of what detecting point included in the plurality of detecting points (for example, FA1 to FA9) is used for each of-the plurality of shot areas (212) on the sensitive substrate (W), and when a certain shot area (212) on the sensitive substrate (W) is subjected to scanning exposure, the controller (90) adjusts the surface position of the sensitive substrate (W) by the aid of the substrate-driving system (LS) by using only the detection result for the detecting point determined for the shot area (212). As described above, the detecting point, which is suitable to detect the surface position corresponding to each of the shot areas, is previously determined, and thus it is possible to adjust the surface position (perform the focus/leveling control) with good efficiency and with less error.
It is desirable that the effective area on the sensitive substrate is disposed inside a prohibition zone (pattern prohibition zone) defined over an entire surface of the sensitive substrate (W) or at a circumferential edge portion of the sensitive substrate (W). In this, embodiment, from the point of time at which at least one of the detecting points overlaps the inside of the sensitive substrate or the prohibition zone defined at the circumferential edge portion of the sensitive substrate, the control of the substrate-driving system is started in order to adjust the surface position of the sensitive substrate. Especially, the use of the inside of the prohibition zone defined at the circumferential edge portion of the sensitive substrate makes it difficult to be affected by dust and camber existing in the vicinity of the outer circumference of the sensitive substrate. Therefore, it is possible to detect the surface position of the sensitive substrate more accurately.
Various judgement standards are conceived to make judgement whether or not the area is the effective area. However, it is preferable that the controller (90) judges whether or not any detecting point (FA1 to FA9) for the position-detecting system (151, 161) overlaps the effective area on the sensitive substrate (W), on the basis of positional information on outer circumference of the sensitive substrate (W), positional information on the respective detecting points (for example, FA1 to FA9) for the position-detecting system (151, 161), and positional information on the shot area (212) to be subjected to exposure. Accordingly, it is possible to accurately judge whether or not any of the detecting points for the position-detecting system overlaps the effective area on the sensitive substrate. Thus, it is possible to accurately start the control of the adjustment of the surface position of the sensitive substrate effected by the substrate-driving system.
As another judgement standard to make judgement whether or not the area is the effective area, for example, it is preferable that the controller (90) judges whether or not any of the detecting points (FA1 to FA9) for the position-detecting system (151, 161) overlaps the effective area on the sensitive substrate (W) by comparing a predetermined allowable value with the detection results for the plurality of detecting points (for example, FA1 to FA9) for the position-detecting system (151, 161). In this embodiment, the effective area is judged in accordance with whether or not the detection value is included in the range of the predetermined allowable value. Even in the case of those included in the effective range, if any error factor exists due to any influence of dust or camber of the sensitive substrate, such a factor can be removed provided that it is excluded from the range of the allowable value. Therefore, this embodiment is advantageous in that an unexpected situation can be dealt with.
As for the timing to start adjustment for the inclination of the sensitive substrate by the aid of the substrate-driving system by using the control system, for example, the following procedure is available. That is, it is preferable that when the shot area (212) in the vicinity of the outer circumference of the sensitive substrate (W) is subjected scanning exposure, the controller (90) starts, from a point of time at which a plurality of detecting points (for example, FA1 to FA9) overlap the shot area (212), adjustment for the inclination of the sensitive substrate (W) on the basis of only the detection results for the detecting points (FA1 to FA9) which overlap the shot area (212), by the aid of the substrate-driving system (LS). Accordingly, when the plurality of detecting points overlap the shot area, the inclination of the surface of the shot area can be known. Thus, it is possible to perform the leveling control accurately.
Various judgement standards are conceived to judge whether or not any detecting point for the position-detecting system overlaps any shot area. However, it is preferable that the controller (90) judges whether or not any detecting point for the position-detecting system (151, 161) overlaps the shot area (212), on the basis of positional information on outer circumference of the sensitive substrate (W), positional information on the respective detecting points (for example, FA1 to FA9) for the position-detecting system (151, 161), and positional information on the shot area (212) to be subjected to exposure. Accordingly, it is possible to accurately judge whether or not any of the detecting points for the position-detecting system overlaps any shot area on the sensitive substrate. Thus, in the inventions, it is possible to accurately judge the number of detecting points overlapping the shot area. Alternatively, it is preferable that when the shot area (212) in the vicinity of the outer circumference of the sensitive substrate (W) is subjected to scanning exposure, if only one detecting point (for example, FA1 to FA9) overlaps the shot area (212), then the controller (90) starts adjustment for the inclination of the sensitive substrate (W) by the aid of the substrate-driving system (LS) on the basis of detection results for a predetermined number of detecting points (FA1 to FA9) including the only one detecting point (one point included in FA1 to FA9) and at least one detecting point (adjoining point included in FA1 to FA9) adjacent thereto, and then the detecting point (FA1 to FA9) to be used for the adjustment for the inclination is successively shifted toward the inside of the shot area (212). Even when only one detecting point overlaps the shot area, the adjustment for the inclination of the sensitive substrate is started on the basis of the detection results for the detecting points including at least one detecting point adjacent to the one detecting point, and the detecting point to be used for the inclination adjustment is successively shifted toward the inside of the shot area, in accordance with the increase in the number of detecting points disposed at the inside of the shot area. Thus, it is possible to perform the adjustment for the inclination more accurately.
According to the seventeenth aspect of the present invention, there is provided a scanning exposure method for exposing a sensitive substrate (W) with an image of a pattern formed on a mask (R) by moving the sensitive substrate (W) in a scanning direction with respect to an exposure area (IF) which is conjugate to an illumination area (IA) illuminated with an illumination light beam (EL), in synchronization with movement of the mask (R) in the scanning direction with respect to the illumination area (IA), the scanning exposure method comprising the steps of:
projecting a plurality of slit images onto a surface of the sensitive substrate (W) in a direction inclined by a predetermined angle so that the plurality of slit images are arranged along a non-scanning direction in detecting areas (ABE, AFE) having a width in the non-scanning direction perpendicular to the scanning direction wider than that of an exposure area (IF) and disposed on one side and the other side in the scanning direction with respect to the exposure area (IF) during scanning exposure for the sensitive substrate (W);
receiving reflected light beams of the respective slit images coming from the sensitive substrate (W) to calculate, on the basis of photoelectrically converted signals thereof, relative-positions on the surface of the sensitive substrate (W) with respect to a predetermined reference plane at respective detecting points a(for example, AF1 to AF9) onto which the slit images are projected respectively; and adjusting a surface position of the sensitive substrate (W) in the exposure area (IF) on the basis of a result of the calculation.
According to the scanning exposure method, the plurality of slit images are projected onto the surface of the sensitive substrate in the direction inclined by the predetermined angle so that the plurality of slit images are arranged along the non-scanning direction in the detecting areas having a width, in the non-scanning direction perpendicular to the scanning direction, wider than that of the exposure area, and disposed on one side and the other side in the scanning direction with respect to the exposure area, during scanning exposure for the sensitive substrate. The reflected light beams of the respective slit images coming from the sensitive substrate are received to obtain the photoelectrically converted signals on the basis of which the relative positions of the surface of the sensitive substrate with respect to the predetermined reference plane are calculated respectively at the respective detecting points onto which the slit images are projected. Further, the surface position of the sensitive substrate in the exposure area is adjusted on the basis of the result of the calculation. Accordingly, for example, when the scanning is performed from the outside to the inside of the sensitive substrate upon exposure for the area in the vicinity of the outer circumference of the sensitive substrate, it is possible to calculate the relative position of the surface of the sensitive substrate with respect to the predetermined reference plane at the detecting point on the basis of the photoelectrically converted signal of the reflected light beam of the slit image at the detecting point protruding over the outside of the exposure area. As a result, it is possible to calculate the relative position of the surface of the sensitive substrate at the adjacent portion with respect to the predetermined reference plane by using the detecting point protruding over the outside of the exposure area. It is possible to adjust the surface position of the sensitive substrate on the basis of the result of the calculation. Therefore, it is possible to avoid the decrease in throughput which would by otherwise caused by the change in scanning direction for the sensitive substrate, and it is possible to perform the focus control more accurately by utilizing the calculated data.
According to the eighteenth aspect of the present invention, there is provided a projection exposure method for exposing a plurality of shot areas (210) on a sensitive substrate (W1 or W2) respectively with an image of a pattern formed on a mask (R) via a projection optical system (PL) by moving the sensitive substrate (W1 or W2) in a scanning direction with respect to an exposure area (IF) which is conjugate to an illumination area (IA) illuminated with an illumination light beam (EL), in synchronization with movement of the mask (R) in the scanning direction with respect to the illumination area (IA), the projection exposure method characterized by comprising the steps of:
selecting some of the plurality of shot areas (210) as sample shot areas so as to include shot areas (210) in the vicinity of outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate (W1 or W2) with respect to the exposure area (IF);
measuring coordinate positions of the sample shot areas respectively;
detecting a relative position of the sensitive substrate (W1 or W2) with respect to a predetermined reference plane for each of the sample shot areas when the coordinate positions of the sample shot areas are measured;
determining an arrangement of the plurality of shot areas (210) on the sensitive substrate (W1 or W2) on the basis of the measured coordinate positions of the sample shot areas;
performing positional adjustment of the respective shot areas with respect to the image of the pattern on the mask (R) on the basis of the determined arrangement of the shot areas (210) while adjusting a surface position of the sensitive substrate (W1 or W2) on-the basis of the relative position detected by measuring the coordinate positions, when exposure are performed for the respective shot areas (210) in the vicinity of the outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate (W1 or W2) with respect to the exposure area (IF).
According to the projection exposure apparatus, some of the plurality of shot areas are selected as the sample shot areas so as to include the shot areas in the vicinity of the outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate with respect to the exposure area, of the plurality of shot areas on the sensitive substrate. The coordinate positions of the some of sample shot areas are measured respectively. The relative position of the sensitive substrate with respect to the predetermined reference plane for each of the some of sample shot areas is detected when the coordinate positions of tie some of sample shot areas are measured. After that, the arrangement of the plurality of shot areas on the sensitive substrate is determined on the basis of the measured coordinate positions of the sample shot areas.
The positional adjustment with respect to the image of the pattern on the mask is performed for the shot area on the basis of the determined arrangement of the shot areas as described above when exposure is performed for the respective shot areas in the vicinity of the outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate with respect to the exposure area, and the surface position of the sensitive substrate is adjusted on the basis of the detected relative position by measuring the coordinate positions.
Accordingly, even in the case of exposure for the respective shot areas in the vicinity of the outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate with respect to the exposure area, it is possible to adjust the surface position of the sensitive substrate on the basis of the relative position detected when the coordinate position is measured. Therefore, it is possible to avoid an inconvenience that the scanning direction is changed from the inside to the outside upon exposure for such shot areas, and the throughput is sacrificed.
In this aspect, it is not necessarily indispensable that the sensitive substrate is moved in the same direction as that during the exposure to detect the relative position of the sensitive substrate with respect to the predetermined reference plane, when the coordinate position of the sample shot area in the vicinity of the outer circumference is measured. However, it is desirable that the relative position of the sensitive substrate (W1 or W2) with respect to the predetermined reference plane is detected while moving the sensitive substrate (W1 or W2) in the same direction as that used during exposure upon the measurement of the coordinate positions of the shot areas (210) in the vicinity of the outer circumference which are set to be subjected to scanning from the outside to the inside of the sensitive substrate (W1 or W2) with respect to the exposure area (IF), of the sample shot areas, because of the following reason. That is, by doing so, it is possible to perform focus control in which, for example, the offset, which depends on the movement direction of the sensitive substrate (W1 or W2), is removed.
The exposure apparatus, the projection exposure apparatus and the exposure method of those aspects described above are extremely effective for the step and scan type projection exposure, especially suitable for performing the double exposure in which high resolution is required in exposure.